To prepare the cake:

1. Heat oven to 350 degrees F.
2. Butter and flour four 9-inch cake pans.
3. In a large bowl, whisk together flour, baking powder and salt.
4. In another large bowl, whisk together butter, sugar, milk, vanilla, and eggs.
5. Pour wet ingredients over dry ingredients. Stir together just until combined; let sit for 15 minutes.
6. Stir batter until smooth.
7. Divide half of the batter evenly among the four prepared cake pans.
8. Bake cakes for 15 minutes rotating halfway through; they should be barely browned.
9. Let cakes cool in pans for 20 minutes before inverting onto wire racks.
10. Clean and dry pans.
11. Repeat the process of greasing and flouring pans, baking four more cakes, and allowing them to cool completely.

To prepare the icing:

1. In a large saucepan over medium-high heat, bring chocolates, sugar, milk and butter to a boil.
2. Stir frequently until mixture is smooth, approximately 8 minutes.
3. Stir in vanilla, and remove from heat.
4. Allow icing to thicken for 30 minutes.

To assemble the cake:

1. Place one cake on a cake stand. Spread with 1/4 cup of icing.
2. Repeat with remaining cakes leaving the top and sides uniced.
3. Chill cake for 30 minutes.
4. Reheat remaining icing as needed before icing the top and sides.
5. Refrigerate, and serve cool.