Line a 12 cavity muffin tin with muffin liners (or spray with non stick spray). Preheat the oven to 360°F.
Combine the flour, cocoa powder, baking powder, baking soda and salt in a large bowl.
In a separate smaller bowl, whisk together the oil, mashed bananas, sugar, egg, milk and vanilla extract. Pour these wet ingredients into the bowl with the flour mix and fold together with a spatula until just combined. A few lumps are OKI!
Fold in the chocolate chips. Evenly distribute the batter between the prepared muffin cups. (There are about 3 tablespoons of batter per muffin.)
Bake in the preheated oven for 18-20 minutes, or until a toothpick inserted in the middle of a muffin comes out clean. Cool in the pan for 5 minutes, then remove onto a cooling rack to cool completely.
Any kind of mild oil works well in these muffins. Canola or melted coconut oil are our favorites. Melted butter works, too!