Quickly blend part of the oats. Add 1 cup of oats to a blender or food processor and pulse into a coarse flour.
Leave the remaining 1/2 cup oats whole for texture.
Mix the wet ingredients. In a medium bowl, stir together the nut butter, maple syrup (or honey), and vanilla until smooth and glossy.
Add the dry ingredients. Stir in the oat flour, remaining whole oats, ground flaxseed, salt, and cinnamon (if using). The mixture should start to look like cookie dough.
Adjust consistency. If the mixture feels too dry or crumbly, add milk 1 teaspoon at a time until it holds together when pressed. If too sticky, sprinkle in a bit more oat flour.
Fold in the chocolate chips. Use mini chips for even distribution.
Press them in gently to avoid melting.
Chill briefly. Pop the bowl in the fridge for 15–20 minutes. This makes rolling easier and helps flavors blend.
Roll into bites. Scoop about 1 tablespoon per bite and roll between your palms. Aim for 16–20 bites, depending on size.
Optional finishing touches. Roll in crushed nuts, shredded coconut, or a dusting of cocoa powder if you like.
Set and serve. Enjoy right away, or chill 10 more minutes for a firmer texture.