My partner and I were in Napier over the Christmas period and visited Mister D, a restaurant/café/bar in town. They serve the most delicious fresh doughnuts amoung other things. We could see one of the staff kneading dough and making a new batch on the counter (which you can see in my drawing). The filling comes in a syringe so you can inject it in yourself. Raspberry, chocolate or custard from memory. We had custard.