In a large microwave safe bowl, microwave the butter until melted.
Add both sugars and stir until the sugars are incorporated. Chill the mixture for 10 minutes.
Remove from the refrigerator and stir in the egg, egg yolk, and vanilla.
Add the flour, oats, baking soda,and salt; mix till combined.Stir in the chocolate chunks.
Chill dough 30 minutes,
Scoop out large tablespoonfuls of dough and place on parchment lined cookie sheets leaving about 2-inches between each cookie.
Bake 325F. 12-15 minutes, or until golden brown.
Cool for several minutes on pan, then transfer to cooling rack.
Yield: 24-36 cookies, depending on size
Adapted from That Skinny Chick Can Bake via The Cooking Channel