Prompt: Chocolate cake recipe
Response:

Ingredients:

1 cup (2 sticks) unsalted butter, at room temperature
2 cups granulated sugar
4 large eggs
2 teaspoons pure vanilla extract
2 cups all-purpose flour
2 teaspoons baking powder
1/2 teaspoon baking soda
1/2 teaspoon salt
1/2 cup whole milk
2 tablespoons unsweetened cocoa powder

For the frosting:

8 ounces unsweetened chocolate, chopped
1/2 cup (1 stick) unsalted butter, at room temperature
1/2 cup granulated sugar
1 large egg
1 teaspoon pure vanilla extract
2 cups all-purpose flour
2 teaspoons baking powder
1/2 teaspoon baking soda
1/2 teaspoon salt
1 cup whole milk
1 tablespoon unsweetened cocoa powder

Directions:

1. Preheat oven to 350 degrees F (175 degrees C). Butter and sugar a 9-inch cake pan, then line the bottom with parchment paper.

2. In a large bowl, cream butter and sugar together until light and fluffy. Add eggs, one at a time, mixing until each is well blended before adding the next. Add vanilla, and mix until combined.

3. In a small bowl, whisk together flour, baking powder, baking soda, and salt. Add to the butter mixture, mixing well until all ingredients are well blended. Add whole milk and mix until batter is smooth.

4. Pour batter into the prepared cake pan. Bake for 25 minutes, or until a toothpick inserted into the center comes out clean. Cool cake in the pan on a wire rack before frosting.

5. For the frosting, melt chocolate and butter in a double boiler over medium heat, stirring occasionally. Remove from heat and add sugar. Stir until smooth. Add egg and vanilla, mixing until combined. Stir in all-purpose flour, baking powder, and baking soda. Add salt, and mix until well blended.

6. Frost cake with frosting, and let cool completely before serving.