Preheat the oven to 180C/Gas4; lightly brush a 12-hole muffin tin with oil; put all the Muffin ingredients – except the jam or chocolate spread – into a large mixing bowl and beat until smooth
Add about 2 spoonfuls of the mixture into each muffin hole, leaving the rest of the mixture for the top; make a dip in the centre of each muffin with a teaspoon, but take care not to go too deep or the jam will come out of the bottom; add a rounded tablespoon of jam or chocolate spread to each one; top with a little more cake mixture and spread it out to make sure that the filling is covered
Bake for 20-25 minutes until risen, golden and just firm to the touch
Mix the sugar with the cinnamon and spread out on a plate, let the cooked muffins rest in the tin for a few minutes before removing them and while still warm, roll them gently in the sugar mixture to coat; leave to cool on a wire rack – don’t eat them straight from the oven as the jam will be very hot
12 servings