Banana Cake with Chocolate Frosting

Cake:
2 C flour
1 tsp baking soda
1 tsp baking powder
1/4 tsp salt
3/4 C butter, softened
1 1/2 C sugar
3 eggs, lightly beaten
1 tsp vanilla extract
1/2 C buttermilk
1 1/2 C mashed ripe bananas

Frosting:
1/2 C butter
1/3 C cocoa
1/3 C evaporated milk or half-and-half
4 C sifted confectioner's sugar
1 tsp vanilla extract

Heat oven to 350. Grease and flour two 9-inch round cake pans. Combine the flour, baking soda, baking powder and salt in a medium bowl, and stir with a fork to combine well.
In a large bowl, combine the butter and sugar, and beat well, about two minutes. Add the eggs, one by one, and then the vanilla. Beat well for two to three minutes more, scraping the bowl occasionally, until you have a smooth batter.
Using a large spoon or spatula, stir in half the flour just until it disappears into the batter. Stir in the buttermilk, and then the remaining flour, the same way. Quickly and gently fold in the mashed bananas, and then divide the batter between the two cake pans.
Bake at 350 for 25-30 minutes, until the cakes are golden brown, spring back when touched in the center and begin to pull away from the sides of the pans.
Cool for 10 minutes in the pans on wire racks or folded kitchen towels. Then turn out onto wire racks or plates to cool completely, top side up.
To make the frosting: In a medium saucepan, combine the butter, cocoa and evaporated milk. Place over medium heat and bring to a gentle boil. Cook, stirring often, for about five minutes, until the cocoa dissolves into a dark, shiny essence. Remove from the heat and stir in the confectioner's sugar and vanilla. Beat with a mixer at low speed until you have a smooth, thick frosting.
To complete the cake, place one layer, top side down, on a cake plate or serving plate, and spread about one cup of frosting evenly over the top. Cover with the second layer, placed top side up. Spread the frosting evenly, first over the sides and then covering the top of the cake. Serves 8-10.