Preheat your oven to 180°C/ 160°C fan. Grease a loaf tin with butter and line it with parchment.
Melt 125 g unsalted butter with 100 g dark muscovado sugar and 2 t of vanille extract in a small saucepan on medium-low heat until the sugar has melted.
In the meantime mash your bananas in a medium mixing bowl (I use my stand mixer for this, with the balloon whisk attachment).
Pour the melted butter and sugar into the bananas and whisk to combine. Add in the 4 T of whole milk and mix in.
Combine 190 g of self-raising flour with 2 t baking powder in a separate bowl and mix to combine before slowly incorporating it into the banana sugar butter mixture, until fully combined and then gently fold in the egg until fully combined.
Pour the mixture into your loaf tin and top with a sprinkling of 10 gr of roughly chopped dark chocolate and sea salt.
Bake the loaf for 40 minutes to an hour until a skewer comes out absolutely clean. If the loaf looks like it may burn on top before the skewer comes out clean, cover it with foil and continue baking.
Remove from the oven once a skewer comes out clean and dry. Leave to cool in the tin for about 5 minutes and then remove. Be sure to have a warm slice because this best banana bread is absolutely divine while still warm.