1. Preheat oven to 350º.
2. Mix butter and sugar together until light and fluffy.
3. Add in vanilla extract.
4. Mix in the eggs, one at a time, mixing until just blended between each egg.
5. Add cocoa powder, flour, baking powder, and salt. Stir until well blended.
6. Bake for 30 to 35 minutes, or until an inserted toothpick comes out mostly clean.
7. Allow to cool for before putting frosting on top.
8. Mix all the buttercream frosting ingredients together until creamy and smooth.
9. Spread evenly over top of cooled brownies.
10. Add ganache ingredients to a small bowl and microwave for 1 minutes. Stir.
11. Microwave in additional 30 second increments, stirring between each, until completely smooth.
12. Pour over frosting and spread evenly.
13. Allow brownies to rest until the ganache has hardened.