Preheat oven to 375 degrees F. Line three baking sheets with parchment paper.
lend the oats in a food processor or blender to a fine powder. In a medium bowl, whisk together the blended oats with the flour, baking powder, baking soda and salt; set aside.
In the bowl of an electric mixer, cream together the butter and both sugars until light and fluffy, 3-4 minutes. Scrape down the sides of the bowl and beat in the eggs one at a time, beating well after each addition. Beat in the vanilla extract. Reduce the mixer speed to low and gradually add the flour mixture, beating just until incorporated. With a rubber spatula, fold in the chocolate chips, grated chocolate and walnuts.
Roll the dough into 2-ounce balls (or about 2 heaping tablespoonfuls worth) and place about 2 inches apart on the baking sheets. Bake one sheet at a time until the edges are set but the center still looks undone, about 10 minutes. Cool the cookies completely on the baking sheets. The cookies can be stored in an airtight container at room temperature for up to 4 days (they can also be frozen for up to 2 months).