- 16 tablespoons (2 sticks) unsalted butter, softened
- 2 cups granulated sugar
- 1 cup unsweetened cocoa powder, sifted after measuring
- 1 cup light corn syrup
- 2 teaspoons vanilla extract
- 4 large eggs
- 2 cups all-purpose flour
- 8 ounces white chocolate, cut into ½-inch chunks
- One 9 × 13 × 2-inch pan, buttered and lined with buttered parchment or foil
- Set a rack in the middle level of the oven and preheat to 350 degrees.
- In the bowl of a standing electric mixer fitted with the paddle attachment, beat together the butter and sugar on medium speed. When they are combined, lower speed as far as you can and add the cocoa, corn syrup, and vanilla extract. Increase speed to medium again and beat until the mixture is lightened, about 3 minutes. Add the eggs one at a time, beating smooth after each addition. Lower the speed again and beat in flour.
- Remove the bowl from the mixer and mix for a moment with a large rubber spatula. Fold in a little more than half the white chocolate pieces.
- Scrape the batter into the prepared pan and smooth the top with an offset spatula.
- Bake the cake for about 40 to 50 minutes, or until a toothpick or a small knife inserted into the center emerges clean. Remove the pan from the oven and immediately scatter the remaining white chocolate pieces over the top of the cake. Return the pan to the oven for 1 to 3 minutes so that the white chocolate melts and crusts slightly. Cool completely on a rack.
- Wrap and refrigerate the pan so that the cake solidifies completely—at least 4 hours; overnight is best. This also makes the cake easier to cut.
- Transfer the whole cake to a cutting board and slide a long knife or spatula under it to loosen the paper or foil, then pull it away. Use a ruler to mark, then cut the cake into 2-inch squares.
- For up to several days, store the brownies between sheets of parchment or wax paper in a tin or plastic container with a tight-fitting cover. Freeze for longer storage. If you plan to keep the brownies for any length of time, it is better to wrap them individually in cellophane.