1. for the pancakes: In a bowl, combine the corn, rice and potato flour with the salt. Gradually beat in the milk, a little at a time until the mixture is smooth.
2. Add the eggs and beat well. Melt a little butter in a hot frying pan, then ladle out a large tablespoon of batter (6 inches in diameter).
3. Cook each pancake over medium heat for about 1 min. on each side, or until golden. Cook the rest of the pancakes, melting a little butter in the pan before each one.
4. Give the batter a good stir with a whisk between each pancake, as the flour tends to sink to the bottom. Roll the pancakes up individually and sprinkle with powdered sugar.
5. For the passion fruit yogurt: Cut the passion fruits in half and scoop out the pulp. Combine with the yogurt and serve with the pancakes.