What’s a girl to do with a bowl of leftover buttercream, namely of the brown sugar variety? Admittedly, my first thought was to grab a spoon and draw the shades, with no one the wiser. But even I don’t have the fortitude for that. So I whipped up a frosting delivery device — in the form of fudgy brownies swirled wth fleur de sel caramel (a small jar was floating in the back of my fridge) — to take care of the excess. A perfect compliment.