Gather the ingredients.
In the bowl of a stand mixer, stir together the flour, sugar, yeast, and salt. Add the water and milk. Using the dough hook, mix on low speed until blended.
Turn the mixer up one speed. Add the butter, 1 tablespoon at a time, while kneading for about 4 minutes, until the dough cleans the bowl.
Turn the dough out onto a lightly floured board and roll it out into a rectangle, about 9 by 12 inches.
Place the dough onto a baking sheet lined with parchment paper. Cover with a lint-free towel and a loose piece of plastic wrap to prevent drying. Let rest at room temperature for 1 1/2 hours, then transfer to the refrigerator for 1 hour.
Line an 8-by-8-inch square dish with plastic wrap. Add 1 cup of soft butter and top it with a second piece of plastic. Press the butter into a flat square. Keep cool in the refrigerator while the dough rests. When it’s needed, the butter should be cold but a little soft and pliable; you may need to take it out 15 minutes before the dough is ready.