Make the dough 

1. In a small bowl, stir together ¼ cup (60 g) lukewarm water (110°F), 1 teaspoon (3.5 g) active dry yeast (about ½ packet), and a pinch of granulated sugar. Let stand until foamy, about 10 minutes. If it doesn’t foam, the yeast may be inactive; start again with a fresh packet.
2. In a large bowl, whisk together ½ cup (120 g) lukewarm whole milk (110°F), 2 tablespoons (28 g) melted and cooled unsalted butter, 2 tablespoons (25 g) sugar, 1 large beaten egg (50 g), and 1 teaspoon kosher salt. Stir in the yeast mixture.
3. Add 1½ cups (195 g) all-purpose flour and mix with a wooden spoon until shaggy. Gradually add the remaining 1½ cups (195 g) flour.
4. If kneading by hand, turn the dough out onto a lightly floured surface and knead until soft and smooth, 5 to 6 minutes. If using a stand mixer fitted with a dough hook, knead on medium speed for 3 to 4 minutes.
5. Shape the dough into a ball and place it in a lightly oiled bowl. Cover and let rise in a warm spot until doubled in size, about 1½ hours (longer if your kitchen is cool).

Make the filling 

1. In a medium bowl, mix 7 tablespoons (100 g) very soft unsalted butter, ⅔ cup (130 g) packed dark brown sugar, 2 tablespoons ground cinnamon, ½ teaspoon kosher salt, ½ teaspoon vanilla extract, ¼ teaspoon each nutmeg, cardamom, and allspice, and 1 tablespoon (8 g) flour into a smooth paste. If the filling feels too firm, give it a 5-second microwave blast – it should be spreadable but not melted.

Assemble

1. Gently punch down the risen dough. On a lightly floured surface, use a rolling pin to roll the dough into a 12×16-inch rectangle. If it resists stretching, let it rest for 5 minutes, then continue – this relaxes the gluten.
   
2. Spread the filling evenly over the dough, leaving a ½-inch border on all sides to prevent the filling from squeezing out as you roll.
   
3. Starting from one of the long edges, roll the dough up tightly but gently into a log. Pinch the seam closed to seal. Place it seam-side down on a parchment-lined baking sheet. Refrigerate the log for 10 to 15 minutes, just until the dough feels slightly firm to the touch. This makes slicing much cleaner and easier.
   
4. Using a sharp knife or bench scraper, cut the log in half lengthwise to reveal the beautiful layers inside.
   
5. Turn the cut sides so they’re facing up. Pinch the top ends together. Lay one strand over the other, then repeat 2 to 3 times, twisting gently as you go so the cut layers remain visible on the outside. Pinch the bottom ends to seal.
   
6. Coil the twisted rope into a spiral, tucking the ends underneath to hold the shape. Carefully transfer it to a 9-inch round cake pan with a parchment-lined bottom and lightly greased sides.
7. Cover loosely with plastic wrap or a clean kitchen towel and let rise in a warm spot until puffy and expanded, about 45 to 60 minutes – it does not need to completely fill the pan. It’s ready when the dough springs back slowly after a gentle press with your fingertip.

Bake the cake

1. Preheat the oven to 350°F. In a small bowl, whisk together 1 large egg with 1 tablespoon milk or cream for the wash. Brush gently over the dough. 
2. Bake for 30 to 35 minutes, until golden brown and the center registers 190–195°F. If it’s browning too quickly, tent loosely with foil halfway through.
3. Cool in the pan for 10 minutes, then lift out carefully and place on a serving platter.

To serve

1. In a small bowl, whisk together ¾ cup (90 g) powdered sugar, ½ cup (115 g) room-temp sour cream, ½ teaspoon vanilla, 1 teaspoon lemon juice, 1 teaspoon zest, and a pinch of salt until smooth. If it’s too thick to drizzle, add 1 to 2 teaspoons milk until pourable.
2. Serve warm. Cut slices and let everyone drizzle with their desired amount of glaze.