1 For the cupcakes: Preheat the oven to 200°C (180° fan) 400°F gas 6. Place paper cases in a 12-hole bun tin.
2 Sift the flour, baking powder and cinnamon into a mixing bowl. Stir in the sugar.
3 Whisk together the eggs and oil in a separate bowl until frothy, then slowly whisk in the milk.
4 Stir into the dry ingredients until just blended. Gently stir in the blueberries.
5 Spoon into the paper cases and bake for 20 minutes until risen and springy to the touch. Cool in the tins for 5 minutes, then place on a wire rack to cool completely.
6 For the mascarpone cream: beat the butter until soft, then sift in the sugar. Gradually beat in the mascarpone until smooth and creamy.
7 Press the blueberries through a sieve into the mixture and beat well.
8 Spoon into a piping bag and pipe a swirl on each cake.
9 Decorate with blueberries and scatter over the pistachios.