125ml buttermilk(or add 1 tsp of lemon juice to milk and leave for 20 mins)
50g pecans, chopped, plus extra to decorate (optional)
Heat the oven to 190C/170C Fan/gas 5. Line a 12-hole muffin tin with paper cases. Sift together the flour, baking powder, bicarbonate of soda and caster sugar with a big pinch of salt. In a separate bowl mix the melted butter, vanilla extract, eggs, mashed bananas and buttermilk.
Make a well in the centre of the dry ingredients and pour the wet ingredients in. Roughly mix together with a fork, being careful not to over-mix. Scatter in the chopped pecans, if using, then spoon the mixture into the muffin cases. Top with pecan halves, then bake for 20-25 mins, until golden brown. Cool on a wire rack.