Preheat your oven to 190c and line a 12-hole muffin tray with liners/folded parchment paper.
Begin by browning your butter by melting the butter in a pan over medium heat. It will go from melted to then bubbling loudly before going quiet and foamy. Keep stirring until it turns a light amber colour overall but the flecks are dark dark brown, and you can smell chestnuts.
Once browned, pour into a bowl to cool down.
In a bowl, whisk together the melted brown butter and sugars for a minute until thick.
Add in your mashed bananas, eggs, yoghurt, and vanilla.
Once all of your wet ingredients are mixed together, gently stir in the flour, bicarb and salt. Then, fold in the chocolate chunks, reserving around 24 chunks (a handful!) to push on top of each muffin.
Divide the batter into 12 muffins. Into the top of each, press 2 chocolate chunks.
Bake for 20 minutes or until a skewer comes out with a few moist crumbs. Store at room temperature in an air-tight container.