By An Edible Mosaic
Whisk together the hot brown butter & brown sugar in a large bowl. Cool & then whisk in the egg yolk, vanilla, and mashed banana. Stir in all remaining ingredients. Chill the dough & then scoop it into balls on baking trays.
Bake until the cookies are puffed and set along the outside, about 12 to 15 minutes, rotating the trays once halfway through.