Preparing the dough ("la détrempe"):

In the bowl of your stand mixer, add in 1 1/2 cups of milk, 1/4 cup granulated sugar, and 2 1/4 tsp instant yeast. With a paddle attachment, mix this together on medium speed for about 5 minutes to ensure that the yeast gets dissolved. Stop the mixer occasionally to scrape down the bowl as needed. Stop the mixer. Add in 2 tsp salt, 2 cups of all-purpose flour, and 4 tbsp of unsalted European-style butter that's been softened. With a paddle attachment, mix on low-medium speed just until the mixture is combined. Stop the mixer. Scrape down the paddle attachment and the sides of the bowl. Avoid over-mixing.

Add in an additional 2 1/2 cups of all-purpose flour, and continue mixing with the paddle attachment just till the dough starts to pull away from the sides of the bowl. Stop the mixer, and scrape down the paddle attachment and the sides of the bowl. Switch to a dough hook attachment, and knead the dough just till it starts to look smooth. Avoid overworking the dough, as you want to minimize gluten formation and make the dough tough.

Take a clean bowl and lightly grease it. Transfer the smooth dough (called "la détrempe") into the greased bowl and cover with plastic wrap. Leave the dough at room temperature for 1 hour. After 1 hour at room temperature, place it in the fridge and refrigerate for a minimum
of 8 hours to overnight.

Preparing the butter block ("le beurrage"):

When the dough has been in the fridge overnight, prepare the butter to roll into the dough. This is called "le beurrage". Take 24 tbsp (3 sticks) of cold unsalted European-style butter and cut them in half lengthwise, so you end up with 6 pieces of butter.

Take a large piece of parchment paper, and lay it on a clean flat surface. Measure out 8" by 8" on the piece of parchment paper, and fold the sides of the parchment paper up so that you have sort of an 8" by 8" shaped envelope. Your piece of parchment paper should be big enough that the folded-up sides cover the 8" by 8" square completely.

Open up the 8" by 8" shape envelope and place the 6 pieces of butter next to each other in the middle of the parchment paper square. Fold up the sides over the butter to enclose the butter, and turn the square over. Let the butter warm up a bit so that it's malleable.

When the butter has softened a bit, gently roll the butter with a rolling pin till the 6 pieces of butter start to blend into each other. Continue rolling and massaging the butter with a rolling pin till it reaches the edges of the folded parchment paper envelope, so that the butter makes a square that is 8" by 8". Place this in the fridge till ready to use.

Laminating the dough:

Lightly flour a smooth clean surface, and take the détrempe dough out of the fridge and roll it into a square that's 12" by 12". If the dough is too cold/firm to roll, let it sit at room temperature for a few minutes to warm up and soften.

TIP: If you have a half sheet pan, you can use it to approximate a 12" by 12" square. Line the sheet pan with parchment paper. When you've rolled out your dough a bit, place it in the sheet pan and continue to roll out the dough so that it's flush with two of the corners and approximately 12" by 12". Cover this square of dough with plastic wrap and leave it in the fridge for 1 hour for the gluten to relax a bit.

After 1 hour, take this 12" by 12" dough and the 8" by 8" beurrage block out of the fridge. Using a pastry brush, brush off any excess flour from the top surface of the dough. To laminate the dough, the dough and the butter should be cool but also soft and pliable during the lamination process. If either is too firm, let them sit at room temperature a bit to warm up.

NOTE: If you have a digital thermometer, the butter should ideally be between 55 to 60 degrees Fahrenheit (13 to 15 degrees Celsius) when folding and rolling.

Place the 8"x8" square of butter in the middle of the dough at a 45-degree angle by inverting it onto the dough while still on the parchment paper so that it looks like a diamond "beurrage" inside the "détrempe" square. The butter will be somewhat stuck to the parchment paper, so you can use the parchment paper to get the right placement. Then peel off the parchment paper.

Fold the four flaps of dough into the center over the butter, stretching the dough a bit, and pinch the dough together to seal the butter inside.

Lightly flour the counter surface as well as the top of the dough, and with a rolling pin, roll the dough into a rectangle that's 10" by 20". Use the rolling pin to create soft impressions along the dough to stretch the dough evenly into an elongated rectangle. Then roll to even it out. Do your best to make it a perfect 10" by 20" rectangle with straight edges and 90-degree corners. Before folding, use a pastry brush to brush off any excess flour on the top surface (excess flour will prevent the layers from sticking together).

Fold one third of the dough into the center. Pat it down so that the two layers stick together. Brush off any excess flour from the top surface of this fold, and then fold the opposite end over and onto this first fold. This is called a "letter fold", as it's like folding a letter. Again, try to make everything neat and make the edges line up as much as possible.

Pat down the folds a bit to compress the layers together, place it back on a parchment paper-lined sheet pan, cover with plastic wrap, and place it in the fridge for 1 hour for the gluten to relax a bit. The more you manipulate dough, the more gluten is formed, and the dough starts to become too tough to roll out. The 1 hour rest time in the fridge allows the gluten to relax a bit and also for the butter to get cold and firm up again.

After 1 hour in the fridge, take the dough out and let it sit at room temperature for a few minutes to soften and become malleable again. Lightly flour the counter surface as well as the top of the dough. Rolling the longer edge to 20" long, roll it out into a 10" by 20" rectangle again using the same technique as before.

Use a pastry brush to brush off any excess flour on the top surface. Fold the short 10" edges toward the center so that they meet at the center but don't overlap. Brush off any excess flour from the top surface of these folds. Where the edges meet at the center, fold the dough in half like you're closing a book. This is called a "book fold". Gently pat and press the dough a bit to compress the layers together and make sure all the edges are neat and aligned.

Place the dough back on the parchment paper-lined sheet pan, wrap this tightly in plastic wrap, and leave it in the fridge for a minimum of 8 hours to overnight.

Ube Filling:
(can be made in advance, or the day of baking)

In a mixing bowl, add in 1 1/2 cups of ube halaya, 1 tsp of ube extract, and 1/4 tsp of salt. Mix this together until everything is well combined.

Transfer this ube mixture into a disposable piping bag (or Ziploc bag), cut a half-inch size hole at the tip, and set aside at room temperature.

Forming and baking the Pain à l'Ubé:

Take 2 large sheet pans (we use 13" by 18" pans) and line them with parchment paper. Take the dough out of the fridge and divide it in half. Leave one half in the fridge while working on the other half.

Flour a clean flat surface, as well as the top of the dough. With the first half of dough, roll out a rectangle that is 8.5" by 24". Try to keep the edges as straight as possible, and the dough as evenly thick as possible throughout. To ensure the dough isn't sticking to the surface, sprinkle additional flour as needed and feel free to move the dough or flip it while rolling.

When you have your 8.5" by 24" rectangle, using a pizza cutter, cut off about quarter of an inch of dough from the long 24" sides. This will expose the butter layers so they'll be visible when the dough is rolled into rolls.

NOTE: if you don't have a pizza cutter, cut with a knife using straight downward and lifting up cutting motions rather than sawing or dragging motions, which may lock the layers of butter and prevent seeing the definition after baking.

Then with a pizza cutter, cut the 8" side in half down the middle, then cut the 24" side into quarters, resulting in eight smaller rectangles that are 4" by 6". Brush excess flour from both sides of these rectangles so that the dough sticks to itself when rolling.

Take one of the 4" by 6" rectangles, pipe ube filling along one of the 4" ends and again around the halfway mark, then roll it up into a tube. Place it on the prepared sheet pan, seam-side down so it doesn't unroll.

Repeat this with all of the 4" by 6" rectangles, and do the same thing with the other half of the dough in the fridge. Place eight rolls on each sheet pan for a total of 16 rolls.

Loosely cover the rolls with plastic wrap and let them proof at room temperature for 2 hours, until they look very puffy.

After 2 hours of proofing, place racks on the upper and lower third positions of your oven and preheat your oven to 425 F (220 C). While waiting for the oven to preheat, in a small bowl, add in 1 egg and a pinch of kosher salt. Beat together thoroughly then brush the tops and sides of the rolls with this egg wash. Avoid brushing the ends of the rolls with egg wash, as we don't want to lock the layers of butter and prevent seeing definition.

Bake them in your preheated oven at 425 F, one pan on the upper third and one pan on the lower third rack, for 18 to 20 minutes, or until they're golden brown. Let them cool a bit before eating. Enjoy!

These Pain à l'Ubé rolls will keep at room temperature for 3 to 5 days stored in an airtight container.