For the Dough
7 tbsp. unsalted butter
1 1⁄2 cups whole milk, heated to 115°
2 tsp. active dry yeast
4 1⁄2 cups flour, plus more for dusting
1⁄4 cup sugar
1 1⁄2 tsp. cardamom seeds, lightly crushed
1⁄4 tsp. kosher salt
For the Filling and Topping
1⁄2 cup granulated sugar
7 tbsp. unsalted butter, softened
1 tbsp. ground cinnamon
1 1⁄2 tsp. cardamom seeds, finely crushed
1 egg, beaten
Pearl sugar, for topping
Make the dough: Melt butter in a 1-qt. saucepan over medium. Remove from heat and stir in milk and yeast; let sit until foamy, about 10 minutes. Whisk flour, sugar, cardamom, and salt in a bowl. Stir in yeast mixture until dough forms. Transfer dough to a lightly floured surface; knead until smooth and elastic, about 3 minutes. Return dough to bowl and cover with a clean dish towel; let sit in a warm place until dough is doubled in size, about 1 hour.
Make the filling: Mix granulated sugar, butter, cinnamon, and cardamom in a bowl until smooth.
Assemble the bread: On a lightly floured surface, roll dough into an 11″ x 17″ rectangle, about 1⁄4″ thick. Spread filling over dough, leaving a 1⁄2″ border along edges. Working from one long end, roll dough into a tight cylinder; transfer seam side down to a parchment paper-lined baking sheet. Cover with dish towel; let sit in a warm place until dough has doubled in size once more, about 45 minutes.
Bake the bread: Heat oven to 375°. Using kitchen shears and starting 1″ from ends of dough, make crosswise cuts, spaced 1″ apart, three-quarters of the way through dough. Fan dough slices away from the center, alternating left to right. Brush dough with egg and sprinkle with pearl sugar; bake until golden brown, about 22 minutes. Let bread cool completely before serving.