When making the Chocolate Banana Muffins, can the mixture be made in advance, e.g. the day before and then stored overnight in the fridge?
Nigella's Chocolate Banana Muffins (from KITCHEN) have bicarbonate of soda (baking soda) as the leavening agent. Unfortunately, as bicarbonate of soda acts very quickly once it is mixed into liquids it means that the muffins need to be baked as quickly as possible after the batter is mixed. So we would not recommend making the muffin batter in advance and leaving it in the fridge.
The muffins keep very well and you can bake them the day before, store in an airtight container and reheat in a warm oven (150°C/130°C Fan/300°F) for 5-8 minutes before serving. They also freeze well in an airtight container or tightly sealed freezer bag. Leave on a wire rack at room temperature for about 3 hours then warm through as above. If you have to bake them on the day, measure out the dry ingredients and mix them together in a bowl, measure out the oil in a jug and set it aside and put the eggs out ready. Mash the bananas and leave them in the fridge overnight, with a piece of clingfilm (plastic wrap) or baking parchment (parchment paper) pressed on to the surface to stop the surface from browning too much. Remove the banana from the fridge 10-20 minutes before you mix the muffins (when you turn the oven on to heat it) so that it loses its fridge chill, then it will take just a couple of minutes to mix up the muffin batter ready for baking.