Ingredients
1 stick unsalted butter, melted and cooled, plus more, softened, for pans
1 2/3 cups unbleached all- purpose flour
2 teaspoons baking powder
3/4 teaspoon kosher salt (we use Diamond Crystal)
4 large eggs, room temperature
1 1/2 cups sugar
2 teaspoons pure vanilla paste or extract
3/4 cup sour cream, room temperature
10 cream-filled chocolate cookies, such as Oreos, broken into bite-size pieces
Preparation
Preheat oven to 350°F. Brush a 9-by-13-inch or 8-by-12-inch baking pan with butter. Line with parchment, leaving a 2-inch overhang on long sides. Butter parchment.
Whisk together flour, baking powder, and salt. Combine eggs and sugar in the bowl of a mixer fitted with the whisk attachment. Beat on high speed until thick and pale, about 4 minutes. Add flour mixture; beat just to combine. Add butter and vanilla; beat to combine. Add sour cream; beat until smooth.
Scrape batter into prepared pan, smoothing top with a spatula. Sprinkle with cookie pieces. Bake until top springs back when lightly touched and a tester inserted in center comes out clean, 30 to 35 minutes (for 9-by-13-inch) or about 40 minutes (for 8-by-12).
Let cool in pan on a wire rack 10 minutes. Using parchment overhangs, lift out of pan and let cool completely on rack. Cake can be stored at room temperature, wrapped in plastic, up to 1 day.
