Spiced Brown Butter Frosting

When I was a kid, my mom made the best banana bars ever. I remember the first time I helped her make the frosting and how I was totally convinced she was ruining them because she was browning, or in my young mind, burning the butter. When the frosting came together I was amazed at how delicious it was. I had expected it to taste like something my grandpa would like - he likes his toast black, and totally surprised by the nutty rich flavor the brown butter added to the frosting. It's still o