Place your cubed/sliced butter into a light-colored skillet over medium heat. Light-colored pans make it much easier to watch the color change so you don't accidentally burn it.Once the butter melts, It will begin to bubble and foam up. Keep stirring gently with a heat-proof spatula. After about 5 minutes, the sputtering will quiet down. Tiny golden speckles will start forming at the bottom of pan.The second it turns a rich golden-amber brown, pour it out of the hot skillet into a heat-safe bowl. Pop the bowl into your freezer for 15 minutes to chill it down. (This step can be done in advance as well. Whisk together the all-purpose flour and baking soda in a medium mixing bowl. Set them aside.
Add your cooled brown butter and granulated sugar to the bowl of a stand mixer fitted with the paddle attachment (or use a large bowl with a hand mixer). Beat on high speed for 2 full minutes or until the mixture becomes pale and slightly fluffy.
10 Tablespoons Butter, 1 Cup Granulated sugar
Add the egg yolk and vanilla extract. Beat on high speed for another minute until smooth and fully incorporated.Add ½ cup of mashed banana and mix on medium-low just until combined, stopping to scrape down the sides of the bowl once. 1 Egg Yolk, 1 and ½ teaspoons Pure vanilla extract, ½ cup Very ripe Banana
Mix in salt and cinnamon too. I like to mix cinnamon and salt in butter sugar mixture. You can also whisk them with flour if you prefer it that way.
¼ teaspoon Salt, 2 and ½ teaspoons Cinnamon
Dump flour and baking soda into the wet mixture. Turn your mixer to its lowest speed and mix just until the flour disappears. Over-mixing at this stage develops gluten, which will make the cookies tough instead of tender and chewy.
2 Cups All purpose flour, 1 teaspoon Baking Soda
Preheat your oven to 350°F (175°C) and line two large baking sheets with parchment paper. Pour and mix granulated sugar and cinnamon into a small bowl or shallow plate.Using a 1 and ½ tablespoons cookie scoop, portion out round balls of dough. Roll each ball between your palms until smooth, then drop it into the sugar, coating it completely. Space the balls about 2 inches apart on your prepared baking sheets. ⅓ cup Granulated sugar, ½ teaspoon Cinnamon
Bake at 350°F for 12 to 13 minutes. When you pull these cookies out of the oven, they will look puffed up and slightly soft in the center. As the cookies sit on the hot pan outside the oven for 5 minutes, they will settle, collapse slightly, and form crinkles across the top.After a few minutes transfer them to a wire cooling rack to cool completely.