In a crockpot, melt two sticks of butter with 2 cups of whole bean Yukon. Let cook on low for several hours.
Preheat oven to 350 degrees and prepare 2 baking sheets with nonstick spray or parchment paper. Set aside. In a shallow bowl or large plate, combine the light brown sugar and the granulated sugar.
Strain coffee beans from the butter. You should end up with about ¾ cup of butter. In a sauce pan, add the coffee butter and 4 tablespoons of butter. Melt over medium to low heat. Reserve the remaining 4 tablespoons of butter in a medium sized glass bowl. Swirl the pan over the heat until all the butter is melted. Cook until the butter is a dark copper colors and you will start to notice a nutty or toasty aroma. This is a bit more difficult since the coffee alters the color and smell of the butter. Once the butter is browned, pour over the remaining butter in glass bowl and set aside for at least 15 minutes.
While you are waiting for the butter to cool, whisk together the flour, baking soda and baking powder. Set aside.
In a stand mixer, add the dark brown sugar and the browned butter mixture. Beat on high until smooth, about 1-2 minutes. Add kosher salt, egg yolk, egg and vanilla extract. Beat until full combined. Gradually mix the dry ingredients in, being careful not to over mix.
I put the dough in the refrigerator for a few minutes so it's easier to work with. Take a small amount, about 1½ tablespoons, and roll into a ball. Roll the ball of dough in the sugar mixture and place on pan. These cookies will spread a bit, so make sure you leave a few inches between cookies. Bake for 12-13 minutes, let cool on cookie sheet for a few minutes and transfer to a wire rack.
Recipe by the modern barista at https://themodernbarista.com/index.php/2017/03/15/brown-butter-cookies-yukon-blend/