Preheat the oven to 350F, then line a baking sheet with parchment paper and set aside.
In a medium bowl cream the butter, granulated sugar, and brown sugar until smooth and creamy.
3 tablespoon butter, 3 tablespoon brown sugar, 1 tablespoon granulated sugar
Add in the vanilla extract and the egg yolk and mix to combine.
¼ teaspoon vanilla extract, 1 egg yolk
Mix in the flour, baking soda, cornstarch, and salt until the flour mixture disappears. Fold in the chocolate chips and walnuts.
½ cup AP flour, 3 tablespoon cornstarch, ⅛ teaspoon baking soda, ⅛ tablespoon salt
Roll the cookie dough, place it on a baking sheet, top with more chocolate chips if you'd like, and bake in the preheated oven for 14 minutes. Let the cookies cool on the baking sheet for 10-15 minutes before enjoying it!
2 tablespoon chocolate chips, 2 tablespoon walnuts