Preheat the oven to 180C/350F and line 3 baking trays with grease proof paper/silicone mats/a silpat.
Break your bananas up into a large bowl and mash until soft with a fork. You want to get them as smooth as possible with no large lumps of banana, a few little lumps is fine.
Add in the sugar, egg and vanilla extract and whisk until everything is combined and smooth.
Gradually add in the melted butter, while continuing to whisk the mixture. Whisk until smooth.
Add in the flour, bicarbonate of soda, baking powder, salt and chocolate chips. Switch to a spatula/wooden spoon and fold the flour into the mixture until everything is well combined and there are no lumps of flour.
Using a 1.5tbsp cookie scoop, place rounds of dough 2 inches apart - I got 12 on 2 pans and 4 on the last pan.... I also ate quite a bit of dough, so I got 28 cookies, but you could probably get 30 LOL!
Place in the oven for 10-12 minutes (mine took 11) until puffed up, and slightly golden. You want the edges to be a little brown, but them to still be soft in the middle if you touch them.
Leave to cool on the pans before digging in. Banana Chocolate Chip Cookies will keep in an airtight container, at room temperature, for 4 days. As with most things with banana, the flavour will be more intense on the second day.