1 1/2 cups unsweetened cocoa powder, plus more for dusting
1 teaspoon baking powder
1/2 teaspoon salt
2 sticks (1/2 pound) unsalted butter, softened
2 cups sugar
6 large eggs, at room temperature
2 tablespoons light corn syrup
2 teaspoons pure vanilla extract
1/2 cup chopped roasted cashews
Whipped cream and raspberries, for serving
Preheat the oven to 350°. Butter a 9-by-13-inch metal baking pan. In a medium bowl, sift the flour with 1 1/2 cups of cocoa, the baking powder and salt. In a large bowl, beat the butter with the sugar until light and fluffy. Beat in the eggs, 1 at a time, then the corn syrup and vanilla. Using a rubber spatula, fold in the dry ingredients and the cashews.
Scrape the batter into the prepared pan and bake for about 25 minutes, or until just set. Let the cake cool to room temperature in the pan. Sift cocoa over the cake and cut it into squares. Serve with whipped cream and raspberries.