Rhubarb streusel muffins

Preheat oven to 180 C / Gas 4. Grease two 12-hole muffin tins or line with paper cases.

In a medium bowl, stir together the flour, bicarbonate of soda, baking powder and salt. In a separate bowl, beat the dark brown soft sugar, oil, egg, vanilla and buttermilk with an electric mixer until smooth. Pour in the dry ingredients and mix by hand just until blended. Stir in the rhubarb and walnuts. Spoon the batter into the prepared muffin tins, filling almost to the top. In a small bowl, stir together the melted butter, caster sugar and cinnamon; sprinkle about 1 teaspoon of this mixture on top of each muffin.

Bake in the preheated oven until the tops of the muffins spring back when lightly pressed, about 25 minutes. Cool in the tins for at least 10 minutes before removing.