Place the butter in a heavy bottomed sauce pan over medium heat. Cook, swirling the pan, until the butter foams and starts to brown in the bottom. You want a deep golden brown, but don't allow the butter to burn or it will taste bitter. Immediately pour the brown butter into a bowl and scrape the browned on bits as well.
In a stand mixer, beat the banana, vanilla and sugars until smooth. Add the brown butter and mix on medium until combined. Add the yolk and lemon juice and mix. In another bowl, whisk the flour, baking soda and salt. Add the dry ingredients to the mixer and mix on low until just combined. Add the chocolate chips and mix with a rubber spatula to finishing the mixing.
Cover the bowl with plastic wrap and refrigerate for 1 hour. Heat oven to 350 and line baking sheets with parchment. Using a cookie scoop, make balls of dough (I did 6 per sheet) and bake until the edges are browned and the center is set. This was about 8 minutes for me. Cool on the sheets for a few minutes then move to a rack.