Preheat oven to 350 degrees.
Stir both brownie mixes with 1 cup vegetable oil, 4 eggs
and 1/2 cup water in a large bowl.
In a separate bowl, mix strawberry cake mix with 1 cup water, 3 eggs and 1/3 cup vegetable oil. Beat with a mixer on medium for 2 minutes.
Prepare muffin tins for 48 cupcakes.
Spoon 2 tablespoons of the brownie batter in the bottom of each muffin cup.
Top the brownie batter with the strawberry cake batter until the cup is 2/3 full.
Bake for about 20 minutes.
Cool in pans for 10 minutes and then move to racks.
Beat butter with a mixer on medium-high speed until the butter is pale and creamy (about 2 minutes).
Beat confectioner’s sugar into the butter, about 1/2 cup at a time. After each addition, mix and continue until smooth.
Beat in vanilla extract.
Spread cooled cupcakes with the frosting.