Add softened butter and coconut sugar to stand mixer and whisk/beat to combine.
Add vanilla and peanut butter; mix to combine.
Add in egg and mix to combine (don't over-mix).
Combine almond flour, cassava flour, xanthum gum, flax, oats, baking powder and salt to a medium mixing bowl; whisk to to combine.
Using the dough hook on your stand mixer, add in the flour mixture 1/2 at a time. Keep mixing until fully combined.
Use a spoon to fold in the m&ms and chocolate chips.
Spray a cookie sheet with olive or avocado oil and then place approx. 2 tablespoons of dough in your hand at a time, roll into a smooth ball and place on the cookie sheet. Gently press down and flatten a bit with your fingers (cookies don't spread much at all). Repeat until you have about 6 cookies on the sheet.
Bake on middle rack for 9-10 minutes.
Let cool on the hot cookie sheet at 5-10 minutes.
Move to cooling rack to finish cooling.
Notes
Gluten-Free: you can substitute 1 1/4 cup Bob's Red Mill 1-1 Gluten Free Flour for BOTH the cassava and almond flour.
Whole Wheat Flour: you can substitute 1 1/4 cup whole wheat flour for BOTH the cassava and almond flour.
Nut Free: you can either the whole wheat flour or gluten-free flour substitutes above and substitute Sunbutter for the peanut butter.
Coconut Sugar: you could also use 1/2 cup organic cane sugar + 1/2 cup brown sugar here
Peanut Butter: I used this kind of creamy, drippy peanut butter.
Xantham Gum: this is optional, but it helps the cookies stick together more since they are gluten-free. If you are using a regular flour substitution, this can be omitted.
Quick-Cooking Oats: you can make your own quick-cooking oats by pulsing whole rolled oats in a food processor a couple times.