Preheat the oven to 350°F. Line a 12-cup muffin tin with paper liners or lightly grease each cup to prevent sticking.
Place cooked split peas in a blender blend until completely smooth and creamy. If needed, add a tablespoon of milk to help them blend. Measure out 3/4 cup of the puree.
In a medium bowl, whisk together the split pea puree, egg, milk, oil and maple syrup/sugar until smooth and well combined.
Stir in the pancake mix (or flour) and cocoa powder. Mix gently until just combined and no dry pockets remain. Avoid overmixing, which can make the muffins dense.
Fold in the chocolate chips using a spatula.
Fill the muffin cups about 3/4 full with batter. Sprinkle a few extra chocolate chips on top if desired.
Bake for 15–18 minutes, or until a toothpick inserted in the center comes out mostly clean with only a few moist crumbs.
Cool the muffins in the pan for about 5 minutes, then transfer them to a wire rack to cool completely before serving.