1. Preheat oven to 350 degrees Fahrenheit. Line a baking sheet with parchment paper and set aside.
2. Prepare the nut meal (if not using pre-ground almond or hazelnut meal).Add whole hazelnuts or almonds to a food processor and blend until a fine, flour-like texture forms. Weigh or measure out 90 grams (about 1 cup).
3. Add the 90 grams (1 cup) nut meal to the bowl of a food processor along with 1/2 cup chocolate chips. Blend until combined and slightly mealy. The mixture will feel slightly moist from the chocolate.
4. Add the banana, sugar, and coconut oil to the food processor. Blend on high until a smooth, thick batter forms.
5. Transfer the batter to a large mixing bowl.
6. Add the protein powder, cocoa powder, vanilla extract, and salt. Mix with a rubber spatula until fully combined. The batter will thicken into a soft cookie dough consistency.
7. If the dough feels too soft to scoop, roll it loosely into a ball and chill in the refrigerator for 45 minutes or in the freezer for 15 minutes, until firm enough to handle.
8. Scoop and roll dough into golf ball–size balls. Place on the prepared baking sheet. Do not flatten yet.
9. Bake for 8 to 12 minutes or until the edges are set and the centers are just firm. (Baking times will vary depending on protein powder use. See notes).
10. Remove from the oven and gently press each cookie down using your hand or the back of a lightly oiled spoon.
11. Allow cookies to cool completely on the baking sheet while preparing the optional topping.

Optional Chocolate Topping

1. While cookies are cooling, melt 1/2 cup (4 to 6 ounces) dark or dairy-free chocolate in the microwave in short intervals or in a double boiler.
2. Dip half of each cookie into the melted chocolate or drizzle over the top. Sprinkle with chopped nuts if desired. Let chocolate set completely before serving.