Place oats in a food processor or blender and blitz to a coarse powder. Place in a large bowl and sift in the flour, baking soda, baking powder, and salt.
In a separate large bowl, add softened butter and granulated and brown sugars. Beat with an electric mixer until light and fluffy, about 5-7 minutes.
Add the eggs, 1 by 1, followed by the vanilla. Beat for 10-15 seconds after every addition.
Gradually pour the dry ingredients and beat just until well-combined. Gently mix in the chocolate chips, grated chocolate bar, and nuts with a rubber spatula.
Roll the dough into 1-inch balls and place them on a cookie sheet, 2 inches apart. Bake for 10 minutes, or until golden brown.
Allow the cookies to cool on the baking sheet for 10 minutes. Serve warm with a glass of milk. Enjoy!
