Preheat oven to 350. Line 24 muffin cups. In a large bowl mix flour, baking soda, baking powder, and 3/4 tsp salt. Set aside.Melt 1 cup butter in a saucepan. Remove from heat and add Guinness, cocoa powder, instant coffee, and granulated sugar. Stir until smooth.With electric mixer combine brown sugar, and 1 tsp vanilla. Add melted butter mixture and beat on medium until cooled. Beat on low and add eggs one at a time, beating after each additional egg. Bring mixer back to medium speed, alternatively add sour cream and powder mixture - scraping down the sides as needed.Pour batter into liners. Bake for 18-20 minutes. Let cool completely.While cooling let's make frosting!In the electric mixer beat softened butter until creamy. On low speed add in the powdered sugar, liqueur, caramel sauce, and the remaining 1 tsp vanilla. Beat until smooth and fluffy. (This makes a LOT of frosting...)Frost the cupcakes once cooled and enjoy!