Chocolate Cola Cake

Ingredients:

Sponge cake

• Butter, for greasing the pan
• 85 g dark chocolate, chopped
• 1 cup of still cola
• 2 cups of flour
• 1 cup cocoa powder
• 1.5 tsp of baking soda
• 1 teaspoon fine salt
• 2 tbsp. sugar
• 3 large eggs
• 1 cup of sour milk
• 3/4 cup vegetable oil
• 2 tsp vanilla extract

Glaze

• 1 cup of sugar
• 1/2 tsp freshly squeezed lemon juice or 1/4 tsp cream of tartar
• A pinch of fine salt
• 4 large egg whites
• 280 g butter, room temperature, cut into small pieces

Preparation:

1. Biscuit: Place a rack in the lower third of the oven and preheat to 350°F (177°C). Grease and line the bottom of a 9-by-13-inch (23 cm by 33 cm) cake pan with parchment paper. Allow the paper to hang over both sides.
2. Place the chopped chocolate in a bowl. Heat the cola over low heat until it reaches a gentle simmer. Pour it over the chocolate. Let it sit for 5 minutes, then stir until smooth.
3. Whisk the flour, cocoa powder, baking soda, and salt in a medium bowl. Beat the sugar and eggs in a separate bowl with an electric mixer on medium speed until slightly thickened and pale in color, about 3 minutes. Gradually pour in the buttermilk, vegetable oil, vanilla extract, and melted chocolate. Beat on low speed until the ingredients are combined but not air-blended. Pour in the flour mixture and continue beating until combined. Stir gently with a rubber spatula to remove any flour lumps. Pour the batter into the prepared pan. Bake until a light press leaves an indentation and a toothpick inserted into the center comes out clean, about 40 minutes.
4. Without removing the cake, cool it completely on a wire rack. Run a knife around the edge of the pan and invert it onto a wire rack. Carefully remove the parchment paper and cool completely. (The cake can be made ahead of time, wrapped tightly, and stored at room temperature for up to 2 days.)
5. Glaze: Bring a 2-3 inch (5-7 cm) layer of water to a boil in a saucepan that can accommodate the bowl of a stand mixer, ensuring that the bowl is above the liquid. Whisk the sugar, lemon juice, salt, and egg whites in the bowl by hand. Place the bowl over the simmering water and continue whisking until the mixture is hot to the touch and the sugar has dissolved, 1-2 minutes. Place the bowl in a stand mixer fitted with the whisk attachment and beat the whites on medium-high speed until stiff peaks form and the mixture has cooled completely, about 10 minutes. Beat in the butter, a little at a time, until the frosting is smooth and spreadable. (If the frosting separates, simply continue whisking until it becomes smooth again.)
6. Cover the cake with glaze. Serve immediately or store at room temperature for up to 2 hours, refrigerating if necessary. (If refrigerating, allow the cake to come to room temperature for 1 hour before serving.)