So tasty, and gluten-free!
Preheat oven to 350ºF. Prepare 24 paper lined or greased muffin cups (2-1/2 inch).
Melt chocolate in the microwave or according to package directions. Set aside.
Whisk together flour mix, sugar, cocoa powder, baking soda, baking powder and salt in a large mixer bowl. Stir in buttermilk, water, oil, eggs and vanilla and mix for 2 minutes on medium speed. Add melted chocolate and continue mixing for 1 minute.
Portion batter into baking cups filling each almost full. Bake for 20 to 25 minutes or until a wooden pick inserted in the center comes out clean.
Remove from oven and transfer to a cooling rack. Cool to room temperature prior to frosting.
For frosting: Beat butter with an electric mixer on medium-high speed for 1 to 2 minutes until pale and fluffy. Gradually add powdered sugar. Add vanilla and beat until smooth.