Danish Custard and Cinnamon Swirl

Dough

1. Combine the flour (500 g4¼ cups), granulated sugar (50 g¼ cup) and salt (10 g1¾ tsp) in a stand mixer with the dough hook. Dissolve the yeast (6 g2 tsp) in the cold whole milk (260 ml1 cup + 1 tbsp) and add it to the flour with the beaten large egg (1). Mix on low until combined, add the soft butter (60 g¼ cup), and mix until just smooth, stopping as soon as it comes together. Don't knead to a windowpane: the dough should have no dry patches but should tear when stretched.

2. Wrap and refrigerate at least 1 hour; overnight is better.

3. Divide the dough into 2 equal pieces of about 468 g each. Everything through shaping is done once for each piece.

Laminate each piece

1. Butter block. Divide the butter (280 g1¼ cups) into 2 portions of 140 g. Beat one portion, cold from the fridge, between sheets of parchment into a 5 × 5 inch square, just under ⅜ inch thick. Chill it 20 to 30 minutes, not longer. It should be cold but pliable, bending without snapping.

2. Enclose. Roll one piece of dough to 6 × 12 inches. Center the butter block on one half, leaving a ½-inch bare margin on the three open sides. Fold the empty half over like closing a book and pinch the three edges shut.

3. Letter fold. Before rolling, press the pin straight down at 1-inch intervals along the whole package. Roll seam side down to 8 × 18 inches, with steady, even pressure from the center outward. Fold in thirds: bottom third up, top third down. Wrap and chill 30 minutes.

4. Book fold. Roll to 8 × 18 inches again. Fold both short ends in to meet at the center, then close the whole thing like a book. Wrap and chill a full hour before shaping.

Pastry cream

1. Whisk the egg yolks (6), granulated sugar (105 g½ cup) and cornstarch (53 g½ cup) until pale. Heat the whole milk (525 ml2¼ cups) until steaming and pour it slowly into the yolk mixture, whisking constantly. Return to the pan and cook over medium heat, stirring continuously, until very thick and bubbling. Boil for 1 full minute. Stir in the vanilla extract (2¼ tsp). Press plastic wrap onto the surface and refrigerate until fully cold.

Cinnamon filling

1. Make the paste. Whisk the flour (50 g7 tbsp) and whole milk (125 ml½ cup) smooth in a small saucepan. Cook over medium heat, stirring constantly, until it thickens into a stiff, smooth mass that pulls away from the sides, 2 to 3 minutes. Scrape into a bowl, press plastic wrap onto the surface, and cool completely to room temperature. Warm paste melts the butter and breaks the filling.

2. Beat the butter (140 g½ cup + 2 tbsp), brown sugar (300 g1⅓ cups), cinnamon (4½ tbsp) and the pinch of salt until creamy. Beat in the cooled paste in three additions, then the egg white (1). It should be smooth, glossy and spreadable: soft enough to push around with an offset spatula, stiff enough to hold a soft peak.

Shape

1. Heat the oven to 400°F (375°F convection) with a baking steel or stone on the center rack. Give it 45 minutes to heat through.

2. Roll one laminated piece to 14 × 19 inches, about 3.4 mm thick. Rest it 5 minutes if it resists; refrigerate it 10 minutes if it warms as you roll.

3. Spread half of each filling in alternating stripes that run parallel to the 14-inch edges: pipe or spoon bands of cinnamon filling, leaving gaps, then fill the gaps with pastry cream. Leave the last 1 inch at the far 14-inch edge completely bare.

4. Starting at the near 14-inch edge, roll up tightly toward the bare edge, so that 19 inches of dough coils into a log 14 inches long. The bare flap seals the seam. Set the log seam side down, wrap, and chill 20 to 30 minutes.

5. Cut the log into 8 rounds of 1¾ inches with a sharp knife or dental floss. Set them cut side up in well-greased 3-inch muffin cups (a jumbo muffin tin) or individual ring molds. Repeat with the other piece, for 16 swirls in all.

Proof and bake

1. Proof. Tent plastic wrap over the swirls, held up on tall glasses or skewers so it doesn't touch them. Proof at cool room temperature until noticeably puffed, airy, and jiggly when you shake the pan, 2 to 6 hours or more. Go by look and feel, not time; this much butter proofs slowly.

2. Freeze and wash. Freeze the proofed swirls 15 minutes. Whisk the egg (1) with the milk (15 g1 tbsp) and brush it on gently, straight from the freezer, without letting it pool between the layers.

3. Bake. Set the tin directly on the hot steel or stone and bake 8 minutes. Move it to a regular middle rack and bake 12 to 16 minutes more, until deep golden with the filling bubbling. Lean toward the longer time and check the center.

4. Brush at once with the sugar syrup. If you like, drizzle with the icing after 10 minutes of cooling.