In a large bowl, combine the peanut butter, Greek yogurt, and honey (or maple syrup). Mix until smooth and creamy.
Stir in the chocolate protein powder and cocoa powder until fully incorporated. The mixture will begin to thicken.
Add the rolled oats and mix thoroughly until evenly coated and a thick dough forms. If the mixture feels too dry, add 1–2 teaspoons of milk; if too soft, add a tablespoon of oats.
Fold in the dark chocolate chips, reserving a few for topping.
Line an 8×4-inch loaf pan with parchment paper. Transfer the mixture into the pan and press down very firmly to create compact, dense bars. Smooth the top and sprinkle extra chocolate chips over the surface.
Refrigerate for at least 2–3 hours, or until firm. For extra clean slices, freeze for 20 minutes before cutting.
Lift out using the parchment paper and slice into thick bars. Store in an airtight container in the refrigerator.
