Phyllo dough gives this German dessert a light, flaky crust, and raspberries and white chocolate chips contribute to the rich filling. For an extra indulgence, top off Raspberry and White Chocolate Strudel with whipped cream.
Preheat oven to 425ºF. Line a baking sheet with parchment paper. In a bowl, combine raspberries, cornstarch, lemon zest and 4 Tbsp. sugar.
Lay 1 phyllo sheet on a work surface, short side facing you, keeping remaining sheets covered in plastic wrap. Brush sheet lightly with butter and lay a second sheet on top. Repeat with remaining butter and phyllo. (You will have some butter left over.)
Spoon raspberry filling in a 2-inch-thick line along long edge of dough, leaving 2 inches at top and bottom. Sprinkle with white chocolate chips. Roll up tightly, fold ends under, and place seam side down on baking sheet. Brush with a bit of remaining butter. Sprinkle with remaining 1/2 Tbsp. sugar.
Bake until golden brown, 15 to 20 minutes. Let stand on baking sheet on a wire rack for 15 minutes, then slice and serve warm, or let cool and serve at room temperature.