Brookie For One

Ingredients

• tablespoons butter
• tablespoons granulated sugar
• tablespoons all-purpose flour
• tablespoon unsweetened cocoa powder
• large egg yolk
• teaspoon vanilla extract
• tablespoons brown sugar
• tablespoon granulated sugar
• all-purpose flour
• teaspoon baking soda
• teaspoon salt
• semi-sweet chocolate chips
• tablespoons chopped walnuts