Preheat oven to 350°F.
Line 13x9 pan with nonstick foil.
Combine both chocolates and butter in a pot.
Stir over low heat until melted and smooth.
Cool.
In a mixer, beat sugar, eggs, and vanilla extract on high 5 mins.
On low, add flour and salt, then melted chocolate mixture.
Pour in pan and bake 20 mins.
Cool.
Frosting:
Beat peanut butter and butter.
Add powdered sugar and vanilla extract.
Beat well and spread over brownies.
Chill 1 hour and dig in!