Nonstick cooking spray 6 large eggs 3/4 cup granulated sugar 1 teaspoon vanilla extract Pinch kosher salt 3/4 cup all-purpose flour 3 1/2 tablespoons cornstarch 4 tablespoons unsalted butter, melted and cooled 1 tablespoon cocoa powder Powdered sugar, to sprinkle Mascarpone Buttercream: 12 ounces mascarpone 1 1/2 sticks (12 tablespoons) unsalted butter, at room temperature…