Heat the oven to 350°F. Line a 12-cup muffin tin with paper liners or lightly grease each well with cooking spray; set aside.
In a medium bowl mash the ripe banana with a fork until mostly smooth. Add the eggs and maple syrup and whisk until blended and slightly frothy.
If the almond butter is very stiff, warm it briefly (10–15 seconds) in the microwave to soften. Stir the almond butter, almond milk and vanilla into the banana-egg mixture until homogeneous.
In a separate bowl mix the protein powder, baking powder, cinnamon and sea salt. Add the dry mix to the wet ingredients and fold with a spatula until just combined; don’t overmix.
Fold in two-thirds of the chocolate chips, reserving the rest for topping. The batter will be thick but scoopable; add a splash more almond milk if it seems too dense.
Divide the batter among the prepared muffin cups, filling each about three-quarters full. Sprinkle the remaining chocolate chips on top and press gently so they adhere.
Bake for 18–22 minutes, or until the tops are set and a toothpick inserted in the center comes out mostly clean. Rotate the pan halfway through baking for even browning if your oven runs hot.
Let the muffins rest in the tin for 8–10 minutes, then transfer to a wire rack to cool completely. Cooling in the tin helps them finish setting and keeps them moist.