In the bowl of a stand mixer fitted with the paddle attachment, beat bread flour, salt, and remaining 5 tablespoons plus 2½ teaspoons (70 grams) sugar at low speed until combined. Add 6 tablespoons (84 grams) cold butter; beat until mixture resembles coarse crumbs, about 2 minutes. Add remaining 1 cup (227 grams) cold butter; pulse mixer between low speed and “off” just until butter is coated with flour.

Add cold milk to yeast mixture; while pulsing mixer between low speed and “off,” add yeast mixture to flour mixture in a slow, steady stream just until a shaggy dough comes together. (There will still be large pieces of butter.)

Lightly dust work surface with all-purpose flour. Turn out dough onto prepared surface, and shape into a 7-inch square. (Dough will be soft and slightly sticky.) Wrap in plastic wrap, and freeze for 30 minutes.

Lightly dust work surface with all-purpose flour. On prepared surface, roll dough into an 18x9-inch rectangle, lightly dusting surface and top of dough with all-purpose flour as needed. Fold dough in half so short sides meet. Pat fold to mark center. Unfold dough, and pull one short side to center. Pull opposite side to center so short sides are touching. Pinch seams together; fold dough along center seam, like closing a book. Rotate dough 90 degrees; repeat rolling and folding procedure one more time. (Dough will start out soft, rough, and somewhat sticky but will come together; turn dough over as needed so edges are rolled out as evenly as possible.) Wrap in plastic wrap, and freeze for 15 minutes.

Repeat rolling and folding procedure one more time. (If dough is resisting or feels too soft, wrap in plastic wrap and freeze for 10 to 15 minutes before continuing.) Wrap in plastic wrap, and freeze for 30 minutes or refrigerate for 1 hour.

Spray 9 wells of 2 (6-well) popover pans or 2 (6-cup) jumbo muffin pans with baking spray with flour.

Using a pastry brush, brush melted butter onto dough. Sprinkle brown sugar mixture evenly onto butter. Using a sharp knife or pizza cutter, cut dough into 27 (6x2¼-inch) rectangles.

Place 1 dough strip on work surface. Top with another dough strip, staggering so ½ inch of short end of strip extends beyond first strip. Top with a third dough strip, staggering another ½ inch so third strip extends beyond second strip. Starting with bottom strip, gently roll up strips together into a log, pushing center of log up about ⅛ inch. Place in a prepared well. Repeat stacking and rolling procedure with remaining dough. Loosely cover with a piece of greased plastic wrap. (Do not secure plastic wrap. You don’t want to put any weight or pressure on proofed dough.) Let rise in a warm, draft-free place (75°F/24°C) until very puffed and dough jiggles slightly when pan is shaken, 1 to 1½ hours.

Preheat oven to 425°F (220°C).

Place buns in oven; immediately reduce oven temperature to 350°F (180°C).

Bake until golden brown and an instant-read thermometer inserted in center registers 210°F (98°C), 20 to 25 minutes. Let cool in pans for 5 minutes. Remove from pans, and let cool on a wire rack for 10 to 15 minutes.