Line an 8x8-inch pan with parchment paper and set aside.
Add the chocolate chips and coconut oil to a microwave-safe bowl and heat in 20-30 seconds intervals, stirring in between, until melted.
Pour the melted chocolate into the bottom of the pan lined with parchment paper; use a small spatula to spread out evenly. Add to the freezer until the chocolate hardens, about 10 minutes.
Meanwhile to a medium-sized bowl, add the peanut butter, butter, oat flour, oats, protein powder, brown sugar and salt. Mix well to combine. Add 1 tablespoon of milk as needed until you get a dough to form, be careful not to add too much!
Freeze dough for 5-10 minutes (this helps prevent the candy color from coming off the M&M's but you can skip), then fold in half the M&M's.
Add the cookie dough on top of the chocolate layer and spread out evenly/press down well. Add the remainder of the M&M’s across the top and press down one last time.
Place back in the freezer for at least 30 minutes before slicing and enjoy. Keep stored in the freezer.