Preheat your oven to 350°F and line a 12-cup muffin tin with paper liners. These muffins like to stick, so I definitely recommend using liners rather than just greasing the pan.

Let’s start with the streusel since we want it ready to go when our batter is done. In a medium bowl, mix together 1/3 cup flour, brown sugar, and cinnamon. Take cold butter cubes and work them into the dry mixture using your fingertips. Keep pinching and rubbing until you have a crumbly mixture that holds together when you squeeze it – it should look like wet sand with some bigger chunks. Pop this in the fridge while you make the batter.

For the muffins, mash bananas in a large bowl until they’re mostly smooth but still have a few small lumps – this gives the best banana flavor in the finished muffins. Your bananas should be pretty ripe, with lots of brown spots on the peel. Add the melted butter (make sure it’s not too hot), sugar, egg, and vanilla. Whisk until everything’s well combined.

In a separate bowl, whisk together the flour, baking soda, and salt. Add the banana mixture to these dry ingredients and stir just until you don’t see any more flour streaks – you’ll probably need about 12-15 strokes with your spatula. The batter will look a bit lumpy, and that’s exactly what you want. Fold in the chocolate chips with just a few more strokes.

Divide the batter evenly among muffin cups – they should be about 2/3 full. Take your streusel out of the fridge and break it up with your fingers if it’s clumped together. Sprinkle it generously over each muffin, gently pressing it into the batter just a bit so it sticks.

Bake for 20-23 minutes, or until a toothpick inserted into the center of a muffin comes out clean of batter (melted chocolate is okay!). The streusel should be golden brown, and the muffin tops should spring back when you gently press them with your finger.

Let them cool in the pan for about 5 minutes – if you try to move them too soon, the streusel might fall off. Then transfer them to a wire rack to cool completely. Though let’s be honest, these are absolutely amazing while they’re still warm and the chocolate chips are melty!