Heat oven to 190C/170C fan/gas 5.
Lightly grease a 12-hole muffin tin (or use
a silicone one). Put 140g sugar, flour and
bicarb in a bowl and mix to combine. In a
jug, whisk together the yogurt, eggs and
vanilla. Tip the jug contents and melted
butter into the dry ingredients and quickly
fold with a metal spoon to combine.
Divide two-thirds of the mixture
between the muffin holes. Carefully
add 1 tsp jam into the centre of each,
then cover with the remaining mixture.
Bake for 16-18 mins until risen, golden
and springy to touch.
Leave the muffins to cool for 5 mins
before lifting out of the tin and rolling
in the extra sugar.