Preheat oven to 350℉.
(optional) Brown your butter. To make brown butter, heat the butter over medium-low heat in a small saucepan until small brown bits begin to form. Stop once you start to see it turn brown because it is very easy to burn. Set aside to let it cool. It is ok if it solidifies or if you want to refrigerate for future use. Browning butter is not necessary but will greatly improve the flavor of any cookie.
Once the butter has cooled a bit, add dark brown sugar. Stir until the butter is well distributed. Then add in all 3 teaspoons of ube extract. I recommend 2 teaspoons of colored ube extract and 1 teaspoon uncolored ube extract but uncolored is harder to find. Stir until the mixture becomes a uniform color. Add eggs and beat until well incorporated. You can add them one at a time but as long as you beat it well, you can add all three at once.
Mix in the dry ingredients: all purpose flour, baking powder, and salt. Mix until combined.
Break the white chocolate bars into pieces, reserving some on the side for topping. Mix the white chocolate in until its evenly distributed. You can use white chocolate chips instead.
Grease your 9x13 baking pan and pour the batter into it. Top with the reserved white chocolate Bake for 30 to 32 minutes until you think it is done. Cookie bars are supposed to be a bit wetter or denser than regular cookies so use your best judgment. An inserted toothpick won't be clean when removed but bake to your own taste.
Remove from oven and let them cool before digging in and enjoying!
