The not-so secret to the stunning color of this cake is food coloring! I prefer using gel coloring—a little goes a long way—but a double dose of the liquid variety will do as well. I’ve added a twist to the cake’s cream cheese frosting. Folding in some crushed crisp chocolate cookies lends flavor as well as a fun texture to the classic topping.
- Position a rack in the center of the oven and preheat the oven to 350°F (180°C/gas mark 4). Lightly grease and flour the bottom and sides of the half-sheet pan.
- In a small saucepan over medium-low heat, or in a heatproof container in the microwave for 15-second increments, heat the milk and butter together until the butter is melted and the mixture is very hot but not boiling. Stir in the vanilla and the food coloring.
- Combine the flour, cocoa, baking powder, and salt in a medium bowl and whisk until blended. In the bowl of a stand mixer fitted with the whisk attachment, beat the eggs on medium-high speed until pale and foamy, about 3 minutes. Gradually add the sugar and continue beating until a ribbon of batter falls from the beater when lifted, about 3 more minutes.
- With the mixer on medium-low speed, gradually add the flour mixture and mix until just blended, about 15 seconds. With the mixer running, gradually add the hot milk mixture and mix until just blended, about 15 seconds.
- Scrape the batter into the prepared pan and, using an offset spatula, spread evenly. Bake until a toothpick inserted in the center comes out clean, 15 to 17 minutes.
- Let the cake cool in the pan.
- Make the soak: In a small saucepan over medium-low heat, or in a heatproof container in the microwave for 15-second increments, combine the sugar and water and cook until the sugar is dissolved. Set aside to cool to room temperature. (For faster cooling, set the bowl over a larger bowl filled with ice and a little water, stirring frequently.) Store the soak, covered, for up to 2 days in the refrigerator or for up to 3 months in the freezer.
- Make the frosting: In the bowl of a stand mixer fitted with the paddle attachment, beat the cream cheese, confectioners’ sugar, butter, cream, vanilla, and measured salt on medium-high speed until no lumps remain and the texture is light and fluffy, 3 to 4 minutes. Store well covered or in heavy-duty zip-top bags with the air pushed out for up to 1 week in the refrigerator. Before using, bring to room temperature and beat until smooth and light.
- Spread the soak and then the frosting evenly over the cake layer.
- Just before serving, scatter cookie crumbs over the top of the cake, if desired.