Toast the walnuts in the oven at 350 degrees F for 8 to 10 minutes, then chop them. Mash the banana in a big bowl.
Brown the butter, then add it to the bowl with the banana.
Whisk in the remaining wet ingredients. No mixer needed!
Combine the dry ingredients in a bowl, then add them to the wet mixture. Stir until the flour disappears, then add the walnuts.
Bake the banana bread brownies for 22 to 25 minutes at 350 degrees F. Let cool in the pan.
To make the frosting: Brown the butter, then remove it from the heat and slowly add the sugar, then the cream and vanilla. Frost the bars (eat the rest of the frosting off of the spatula), and DIG IN!
