Preheat the oven to 190° (170 fan/ Gas 5/ 375F) and line a 12 hole muffin tin with muffin cases.
Combine the dry ingredients (light brown sugar, caster sugar, plain flour, bicarbonate of soda, ground cinnamon) in a bowl.
Whisk the wet ingredients (natural yogurt, eggs, melted butter) together in a jug then gently mix into the dry ingredients, being careful not to overmix.
Fold in the pumpkin puree.
Spoon the muffin batter into the 12 hole muffin tin lined with muffin cases and bake in a preheated oven for 18 minutes.
Whilst the muffins are cooling, whisk together the frosting ingredients (, and once the muffins cool to touch, drizzle or spread the frosting on and allow to set.