In the bowl of a stand mixer, whisk together milk, egg, egg yolk, and yeast by hand; add flour, sugar, 3 tablespoons (42 grams) butter, and salt. Using the dough hook attachment, beat at low speed until dough comes together, about 1 minute; beat until dough pulls away from sides of bowl and is smooth when a small amount is pinched off, 5 to 8 minutes. Turn out dough onto a lightly floured surface; shape into a smooth ball.
Spray a large bowl with cooking spray. Place dough in bowl, turning to grease top. Cover and let rise in a warm, draftfree place (75°F/24°C) until doubled in size, about 2 hours.
Line a baking sheet with parchment paper. Lightly dust parchment with flour.
Turn out dough onto a lightly floured surface, and gently shape into a 10×8- inch rectangle. Place on prepared pan. Cover tightly with plastic wrap, and refrigerate overnight.
Using a pencil, draw a 12×8-inch rectangle on a sheet of parchment paper; turn parchment over. Place remaining 1 cup plus 1 tablespoon (241 grams) butter on prepared parchment. Cover with a second sheet of parchment.
Using a rolling pin, pound butter to flatten slightly. Using rolling pin and a bench scraper, shape butter to fit inside drawn rectangle, keeping edges straight and even. (If butter gets too soft to work with, refrigerate for 5 minutes before continuing.) Wrap butter fully in parchment paper, and refrigerate for at least 2 hours or overnight.
Freeze dough for 15 to 30 minutes.
Let butter block stand at room temperature until pliable, 10 to 15 minutes.
On a lightly floured surface, roll dough into a 16×12-inch rectangle. Unwrap butter block; place crosswise in center of dough. Fold dough over butter block, meeting in center and stretching and lightly pressing to seal dough around butter block. Rotate dough 90 degrees, and immediately roll into an 18×12-inch rectangle (about ⅛ inch thick). Fold in thirds like a letter; rotate 90 degrees, and roll dough into an 18×12-inch rectangle. Fold in thirds like a letter. Wrap dough in plastic wrap, and freeze for 15 to 30 minutes.
Repeat rolling and folding dough one more time. Wrap dough in plastic wrap, and refrigerate for 1½ hours. (Alternatively, wrap dough tightly in plastic wrap, and freeze for up to 3 months. Let frozen dough thaw overnight in refrigerator before using.)