Make the Cake:

1. Preheat the oven to 350°F (175°C). Grease and flour two 9-inch round cake pans or line them with parchment paper.
2. Sift together flour, sugar, cocoa powder, baking powder, baking soda, and salt in a large bowl.
3. Add eggs, milk, vegetable oil, and vanilla extract to the dry ingredients. Mix on medium speed until smooth, about 2 minutes.
4. Stir in the boiling water until the batter is smooth and thin.
5. Pour the batter evenly into the prepared cake pans and bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean.
6. Cool the cakes in the pans for 10 minutes, then transfer to a wire rack to cool completely.

Make the Ganache Frosting:

1. Heat heavy cream in a small saucepan over medium heat until it simmers. Remove from heat.
2. Stir in the chopped chocolate and butter, mixing until smooth and glossy.
3. Allow the ganache to cool slightly before frosting the cake.

Assemble the Cake:

1. Place one layer of cake on a serving plate and spread a layer of ganache on top.
2. Add the second layer of cake and spread the remaining ganache over the top and sides.
3. Refrigerate the cake for 30 minutes to set the ganache before slicing and serving.