Prepare the blended oats, by placing about 3½ cups of rolled oats into a food processor and blender and process until the oats reach the consistency of flour. Measure 2½ cups blended oatsand place them in a large mixing bowl.
Prepare the ground nuts, by placing about 2½ cups of nuts in a blender or food processor. Pulse the nuts until broken down into very small pieces, being careful to not overprocess. Measure1½ cups ground walnuts and place them in the same bowl as the oats.
Add the 2 cups all-purpose flour, 1 teaspoon baking powder, 1 teaspoon baking soda, and ½ teaspoon table salt to the oats and nuts and mix until well combined. Add 6 ounces dark chocolate chips, 6 ounces semi-sweet chocolate chips, and 4 ounces milk chocolate candy bar (grated) to the flour mixture and toss to lightly coat with flour. Set this mixture aside.
In a large mixing bowl or stand mixer, cream 1 cup unsalted butter with 1 cup granulated sugar and 1 cup light brown sugar until fluffy and light in color, about 7-8 minutes. Add 2 large eggs and 1 teaspoon vanilla extract and beat until well combined.
Add the dry ingredients to the creamed butter and fold together until the flour is fully moistened and just combined. Cover the dough and refrigerate for at least 30 minutes or up to 48 hours.
When ready to bake the cookies, preheat the oven to 375℉ (190℃). Line a baking sheet with parchment paper.
Remove the chilled dough from the refrigerator. Use a medium cookie scoop or 1½ tablespoons for each cookie and then gently roll into even balls. Place the cookie dough onto the prepared baking sheet, spaced 2 inches apart.
Bake the cookies for 6-7 minutes, until the edges are lightly brown and the centers are just a bit soft.
Cool the cookies on the cookie sheet for a minute or two before transferring them to a cooling rack to cool completely.
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Notes
Oats: Use either quick cook or old-fashioned rolled oats, not steel-cut oats. Grated Chocolate: To grate your chocolate, use a hand grater, box grater, or food processor and grate the chocolate bar into small shreds. It works best if your chocolate bar is cold before grating.Note On Chill Time: You need a minimum of 30 minutes to prevent cookies from spreading, but can opt to chill up to 48 hours prior to baking. If you find that your dough is too hard to scoop after chilling for an extended period of time (6+ hours), let it set out at room temperature for 10 minutes to make it easier to scoop. Storing Cookies: Store in an airtight container at room temperature for up to 3 days or in the refrigerator for up to 7 days. You can also opt to flash-freeze the cookies for an hour and then transfer to freezer bag, Store in the freezer up to 1 month and defrost at room temperature.Storing Cookie Dough: Roll into balls as directed, flash-freeze for 1 hour, then store in freezer bag up to 3 months. Bake from frozen 375°F for 8-11 minutes.