In a medium bowl, combine the softened butter and peanut butter. Beat with a hand mixer or stand mixer until smooth and creamy.
Gradually add in the powdered sugar and mix until it’s fully incorporated. The mixture should be thick and dough-like.
Stir in the vanilla extract, salt, and rolled oats. Mix until combined.
Add the mini chocolate chips and M&Ms, and fold them into the dough.
2. Prepare the Fudge Layer:
Line an 8×8-inch or 9×9-inch square baking dish with parchment paper or lightly grease it.
Press the cookie dough mixture into the bottom of the prepared baking dish, spreading it evenly across the bottom.
3. Make the Chocolate Topping:
In a microwave-safe bowl, melt the semi-sweet chocolate chips and 1 tablespoon of butter together. Heat in 20-second intervals, stirring in between, until smooth and completely melted.
Pour the melted chocolate over the cookie dough layer, spreading it evenly with a spatula to cover the entire surface.
4. Chill and Set:
Refrigerate the fudge for at least 2 hours or until the chocolate topping is firm and the fudge has set completely.
5. Slice and Serve:
Once set, remove the fudge from the refrigerator and lift it out of the dish using the parchment paper (if used).
