Black Bean Double Chocolate Muffins

Rinse dried black beans, cover with plenty of cold water and soak overnight (8–12 hours).

Drain and rinse, then cover with fresh water by about 5cm. Don't add salt. Bring to the boil, then simmer for 60–90 minutes until very soft and easily squashed. They need to be softer than you'd cook them for a salad so they blend smooth.

Drain, rinse and cool. Weigh out 240g for the muffins. Cooked beans keep 4 days in the fridge or 3 months frozen. If you end up with less than 240g, make up with extra milk.

Stir the vinegar into the milk and set aside for 5 minutes so it thickens slightly.

In a blender, blend the beans, soured milk, eggs, brown sugar, oil and vanilla for a full minute until completely smooth, with no bean skins visible.

In a large bowl, whisk the flour, cocoa, baking powder, bicarb soda and salt together.

Pour the wet mixture into the dry and fold gently until just combined. A few streaks are fine, since overmixing makes them tough. Fold in most of the chocolate chips.

Rest the batter for 15 minutes while the oven heats to 210°C (190°C fan). Line a 12-hole muffin tin.

Fill the cases right to the top and scatter the remaining chips over.

Bake at 210°C for 5 minutes. Without opening the door, drop to 180°C (160°C fan) and bake another 13–15 minutes, until a skewer comes out with moist crumbs but no wet batter.

Cool in the tin for 5 minutes, then move to a rack. They keep 3 days airtight or 3 months frozen.