Pour 3/4 cup of the whole milk into a saucepan. Heat the milk over low heat until it reaches 90°F. Remove the pan from the heat and pour the milk into a medium-sized mixing bowl. Sprinkle 1/2 teaspoon of the yeast over the milk and stir to dissolve. Working in 1/4 cup increments, stir in 1 1/4 cups of the bread flour. A sticky dough should form. Cover the dough with plastic wrap and set aside to let rise for 2 1/2 hours.
Once the flour mixture has doubled in size, transfer it to a large stand mixer fitted with a dough hook. Add the remaining yeast and set the mixer to it's lowest setting. Let mix for 2 minutes or until the yeast is fully integrated and the dough is uniform. Pour in 3/4 of cup of the remaining milk and increase the mixer's speed. Let mix for 5 minutes or until the mixture resembles a thick cream.
Melt 1 tablespoon of the butter and add it to the mixer. Add the sugar and salt and return the mixer to it's lowest setting. Add 1/2 of the remaining flour in 1/4 cup increments, waiting for each addition to be fully integrated before adding more. Pour the remaining milk into the mixer and mix until integrated. Add the last 1/2 of the flour and mix until a slightly tacky, uniform dough forms.
Place the dough on a well-floured surface and knead it briefly, about 7 minutes. Transfer the dough to a bowl greased with sunflower oil and cover with plastic wrap. Leave the dough to rise for 1 1/2 hours.
Place the dough on a well-floured surface and roll it out into a rectangular shape roughly 2-inches thick. Wrap the dough and transfer it to the fridge and let chill for 3-4 hours.
Once the dough is chilled, take the remaining butter (you should have five sticks) and place them in the center of a large sheet of parchment paper. Place another sheet of parchment paper over top. Using a rolling pin, beat the butter into a rectangular shape that measures 12x18 inches. Transfer the butter to the refrigerator and chill for 20 minutes.
Place the chilled dough on a floured surface and roll it out to a 28x12-inch rectangle. Peel the top sheet of parchment paper off of the chilled butter plate. Place the plate face-side-down on the dough covering 2/3 of it. Peel the the remaining sheet of parchment off of the butter plate. Fold the naked 1/3 of the dough over the butter plate. Continue folding the dough as you would a business letter. Pinch the seams to seal in the butter plate, then give the dough a quarter turn and roll it out to a 28x12-inch rectangle. Fold the dough once again like you would a business letter. Wrap the dough in plastic wrap and transfer it to the refrigerator for 1 hour.
Once the hour has elapsed, return the dough to the floured surface and roll it out to a 28x12-inch rectangle. Fold it again like you would a business letter, then wrap it and return it to the fridge to chill for another hour or until ready to use.