Preheat oven to 350°F/180°C and line two baking trays with parchment paper. Set aside.
Brown the butter: Melt the butter in a medium sized pan over medium heat. Once it melts, it will crackle, then become foamy – continue mixing the butter while this happens to prevent burning. The butter will go from melted to golden brown quickly, and you'll know it's almost done when the aroma of browned butter arrives. The whole process should take about 5 minutes! Once golden, remove from heat and transfer to a glass bowl. Let the butter cool for 30 minutes (Do not let it harden) while you prep on the rest of the recipe.
3/4 cups butter
Once slightly cooled, whisk in the sugar, brown sugar, and brown butter for one minute until combined.
1/2 cup dark brown sugar, 1/4 cup white sugar
Whisk in the egg, egg yolk, vanilla, and maple syrup.
1 egg, 1 tbsp vanilla, 1/4 cup maple syrup
Fold in the flour, baking soda, and salt until just combined. Toss in the chocolate chips and chopped walnuts and fold a few times until incorporated.
1 3/4 cups all-purpose flour, 1/2 tsp baking soda, 1/2 tsp salt
Scoop 6 cookie dough balls on each tray at a time. Bake for 10-12 minutes or until the edges are a light golden brown.
3/4 cups semi-sweet chocolate chips, 1/2 cup chopped walnuts
Top off with additional chocolate and a dash of sea salt if desired. Cool the cookies on a cooling rack and enjoy!