With the leftover cupcakes from the ghosts, it was time to try the penuche frosting. Apparently it's Spanish for "raw sugar" or "brown sugar" and they're absolutely delectable. The frosting is a decadent concoction of brown sugar, butter, and powdered sugar that tastes like toffee. Seriously. For the garnish i chose to coarsely chop up the mini chocolate chips i purchased for the ghosts rather than grate semi-sweet baking chocolate.