Pulse the oats. Add rolled oats to a food processor and pulse 5–8 times until they're partly broken down. You want a mix of oat flour and small flakes for the best bite.
Mix the dry team. In a large bowl, whisk the oats, protein powder, cocoa, and salt. If using espresso powder or cinnamon, add it here.
Warm the binder. In a microwave-safe bowl, gently warm the nut butter and honey/maple for 15–25 seconds until loosened. Stir in vanilla.
Combine wet + dry. Pour the nut butter mixture into the dry ingredients. Stir with a sturdy spatula. Add milk 1 tablespoon at a time until the mixture holds together when pressed—slightly tacky but not sticky.
Fold in the fun. Stir in mini marshmallows and chocolate chips. If it feels too soft, add 1–2 tablespoons more oats. Too dry? Another splash of milk.
Shape the bites. Scoop about 1 1/2 tablespoons per bite and roll into balls. You should get 16–20, depending on size.
Finish like a pro. Roll some in cocoa powder for a truffle vibe, some in crushed freeze-dried marshmallows for extra “hot cocoa” flair, or leave them plain.
Set and chill. Place on a parchment-lined tray and refrigerate 20–30 minutes to firm. That's it. Try not to eat five at once (no promises).