I Want Chocolate chocolate cake

 

I Want Chocolate chocolate cake by Smitten Kitchen

Yield: 1 generously frosted 8×8-inch cake, which we cut into 16 small squares.
Could also yield: 1 generously frosted 8-inch or 9-inch round cake, 12 very generously frosted cupcakes, or it could be doubled and baked in a 9×13-inch pan. Could also be scaled and stacked as a birthday cake.

Cake
6 tablespoons unsalted butter, at room temperature
3/4 cup brown sugar
2 tablespoons sugar
1 large egg
1 large egg yolk
3/4 cup buttermilk
1 teaspoon vanilla extract
1/2 cup Dutch cocoa powder
1 cup all-purpose flour
1/4 teaspoon baking soda
1/2 teaspoon baking powder
1/2 teaspoon table or fine sea salt

Frosting
2 ounces unsweetened chocolate, melted and cooled
1 1/2 cups powdered sugar, sifted
1/2 cup unsalted butter, at room temperature
Pinch of fine sea salt (optional)
1 tablespoons cream or whole milk
1/2 teaspoon vanilla extract

Make the cake: 

• Heat oven to 350°F (175°c).
• Line the bottom of an 8-inch square cake pan with parchment paper, and either butter the parchment and exposed sides of the pan, or spray the interior with a nonstick spray. 
• In a large bowl, use a hand or stand mixer to beat the butter and sugars until fluffy; scrape down bowl. 
• Add the egg, yolk and vanilla and beat until combined, then the buttermilk and mix again. 
• Scrape the bowl down well and don’t worry if the batter looks uneven. 
• Place your flour, cocoa, baking soda, baking powder and salt in a sifter and shake it over the batter bowl. 
• Stir on low until just combined; scrape down bowl a final time. 
• Scoop batter into prepared pan and smooth flat. 
• Bake for 30-40 minutes (for me usually closer to 40), until a toothpick inserted into the center comes out clean. 
• Let cool for 5 to 10 minutes in cake pan on cooling rack, then flip out onto rack or serving plate to completely finish cooling before frosting. 

Make the frosting: 

• Place frosting ingredients in a food processor and run machine to to mix. 
• Scrape down bowl then process for another 1 to 2 minutes just until smooth and somewhat fluffed - don't overbeat, it will soupify!
• Scoop the frosting onto the cooled chocolate cake and swirl it around. 
• Finish with rainbow sprinkles

Cake keeps at room temperature for a day or two, or in the fridge up to a week, or so I’ve heard but never tested out.