01 -
Heat oven to 180°C / 350°F. Line a 12-hole muffin tin with paper cases. Mash the peeled bananas thoroughly in a large bowl.
02 -
Whisk eggs, sugar, oil, 100 ml of the milk and vanilla into the bananas. Mix flour, baking powder and salt separately.
03 -
Fold the dry mixture into the banana mixture just until no dry flour remains. Do not beat the batter.
04 -
Transfer one-third of the batter to a second bowl. Stir cocoa and the remaining 20 ml milk into this portion until evenly combined.
05 -
Divide the plain batter between the 12 cases, add the chocolate batter in small dollops and swirl each once or twice with a skewer. Keep the cases about three-quarters full.
06 -
Bake for 20–24 minutes until the tops spring back lightly and a skewer inserted into the center comes out without wet batter. Cool in the tin for five minutes, then transfer to a rack for another 15 minutes.
07 -
Keep completely cooled muffins airtight for up to two days in a cool room, or freeze for up to two months. Thaw covered at room temperature before serving.