Created by ForeverMama on March 11, 2021
Step 1: In a large bowl, whisk together the flour, baking soda, and salt. Add the oats and stir until the ingredients are evenly combined.
Step 2: In the bowl of an electric mixer fitted with the paddle attachment, beat the butter until smooth and pale in color. Add the sugars and mix on low speed until just incorporated. DO NOT over-mix.
Step 3: Scrape down the bowl and add the eggs, 1 at a time, scraping down the bowl and beating until smooth after each addition, about 20 seconds. Add the vanilla and beat until just incorporated.
Step 4: Scrape down the bowl and add the peanut butter. Mix on low speed until just combined. Add the oat mixture in 3 additions, mixing on low speed until just incorporated.
Step 5: Use a spatula or wooden spoon to fold in the chocolate chunks and M&Ms. Cover the bowl tightly and refrigerate for at least 5 hours (NO LESS).
Step 6: Preheat the oven to 375°F (190°C). Line 2 baking sheets with parchment paper.
Step 7: Use an ice cream scoop to plop 2-tablespoon blobs of dough on the prepared baking sheets, spacing them about 2 inches apart. Gently squash each dough ball. Bake for 12 to 15 minutes, switching and reversing the sheets halfway through the baking time, until the cookies just begin to brown.
Step 8: Let the cookies cool on the baking sheets for 8 to 10 minutes (VERY IMPORTANT TO WAIT. See Note) before gently moving them to a wire rack to cool completely. The cookies can be stored in an airtight container for up to 3 days. Makes 36 cookies.