SERVES 8-10

FOR THE STRUDEL:
12 tbsp. butter, softened
¾ cup confectioners' sugar
1 tbsp. granulated sugar
½ tsp. vanilla extract
¼ tsp. finely grated lemon zest
Pinch fine salt
5 eggs, separated
1 lb. farmers' cheese, mashed to break up any lumps
1½ cups sour cream
¼ cup all-purpose flour
1 recipe strudel dough

FOR THE TOPPING:
2 cups whole milk
½ tsp. vanilla extract
¼ cup confectioners' sugar
3 egg yolks

FOR THE VANILLA SAUCE:
2 cups whole milk
½ cup heavy cream
Pinch fine salt
1 cup confectioners' sugar
1 tsp. vanilla extract
2 tbsp. vanilla pudding mix
3 egg yolks

1. For the strudel: Preheat oven to 400°. Melt 4 tbsp. of the butter in a small skillet over medium-low heat and cook until lightly browned. Pour clarified butter into a small bowl, discarding milk solids. Beat confectioners' sugar and 7 tbsp. of the butter together in a mixing bowl with an electric mixer on medium speed until light and fluffy. Add granulated sugar, vanilla, lemon zest, and salt and beat for 1 minute. Add yolks and beat for 1 minute more. Beat in cheese and sour cream, then beat in flour. In a clean bowl with clean beaters, beat egg whites until soft peaks form. Fold whites into cheese mixture and set aside.

2. Roll and stretch strudel dough out. Position dough and cloth with a longish edge parallel to edge of work surface closest to you. Brush dough with half of clarified butter. Spoon cheese filling along edge of dough closest to you, 3" in from long edge and 1" in from shorter side edges, covering about one-third of the dough. Roll up strudel.

3. Grease a 2" x 10" x 12" baking dish with remaining butter. Using the cloth, lift strudel and tip it into dish, seam side down. Put strudel into dish, curving it to fit without twisting or kinking. Bake for 35 minutes.

4. For the topping: Beat milk, vanilla, sugar, and yolks in a large bowl with an electric mixer on medium speed until frothy. Pour topping over hot strudel in dish and continue baking strudel until topping is golden and no longer jiggly, about 20 minutes more.

5. For the vanilla sauce: Heat half the milk and cream in a heatproof bowl set over a pot of gently boiling water until simmering. Meanwhile, put remaining milk and cream, salt, sugar, vanilla, pudding mix, and yolks into another bowl and whisk until frothy. Whisk custard mixture into hot milk mixture and cook, whisking constantly, until thickened, about 25 minutes.

6. Serve strudel warm, scooped onto plates, with warm vanilla sauce poured on top. Pass around extra vanilla sauce in a pitcher, if you like.