Line a baking sheet or plate with parchment paper or a silicone baking mat. Set aside.
In a large bowl, whisk together the oat flour and protein powder. Using a rubber spatula or wooden spoon, stir in the nut butter, maple syrup, vanilla, and milk. The mixture should be like a cookie dough consistency— come together, but shouldn't be sticky. If it's too dry, add 1 Tablespoon milk. Stir in the chocolate chips, if desired.
Using a cookie scoop or spoon, grab 1.5-2 Tablespoons of dough and roll into balls. Set the rolled balls on the baking sheet or plate as you finish the rest. Store in an airtight container in the refrigerator for up to 1 week.
Make ahead tip: These bites are freezer friendly. Place in an airtight container or bag and freeze for up to 3 months. Thaw overnight in the refrigerator.Oat Flour: If you don't have oat flour, not to worry— it's easy to make! Simply add old-fashioned oats to a food processor or blender until a flour texture. Then, measure out 2 cups.Protein Powder: Use your preferred protein powder, this one and this one are my favorite. If you use a vanilla flavor, decrease the vanilla to 1 teaspoon in the recipe. Depending on the protein powder used, you may need slightly more milk since some soak up more moisture than others.Nut Butter: Any nut butter can be used however depending on the kind can alter the taste. I typically use cashew butter for a more mild taste. If you use a natural butter, be sure to mix it prior and you may need slightly less milk.Milk: I've made these with unsweetened almond milk, oat milk, skim milk, and 1% milk.Chocolate Chips: These are optional (though 100% recommended)— I always go for Enjoy Life brand.