Fill with jam
Using a skewer, pierce a hole in each doughnut, wiggling to make space for the filling. Put 340g smooth strawberry jam in a piping bag fitted with a medium nozzle. Working one at a time, insert the nozzle in the hole of each doughnut and gently squeeze to fill with jam. Put 100g caster sugar on a plate or shallow dish and roll the warm doughnuts in the sugar to coat.
Calories 540 (21.6%), sugar 19.4g (22%), fat 6g (9%), saturates 3.8g (19%), salt 0.09g (2%), based on 25 servings.