Heat oven to 200C/180C fan/gas 6.
Use 1 tsp oil to lightly oil a 12-hole muffin
tin (or use paper cases). Mix both flours
with the baking powder and lemon zest.
Reserve 1 tbsp caster sugar, then stir the
rest into the flour with the muscovado.
Mash the banana well. In another bowl
beat the egg, then stir in the banana,
buttermilk and oil. Using a large metal
spoon, very lightly stir into the flour mix,
just to combine. Over-mixing will make
the muffins tough. Toss in the blueberries
and give just a few turns of the spoon to
carefully stir them in without crushing.
Spoon the mixture into the tin –
each hole should be very full. Bake for
20-25 mins until risen and golden.
Mix the reserved caster sugar with
the lemon juice. When the muffins are
done, remove from the oven, then brush
with the sugar and lemon mixture while
they are still hot. Gently loosen the edges
of each muffin with a knife, then leave
in the tin for 15 mins to cool a little as
they’re very delicate while hot. Remove
to a wire rack. Best eaten the day of
making, but will keep for up to 2 days.