1. Mix in a saucepan, water, sugar, vanilla, and potato flour. Cook on a low heat for a few minutes, stirring constantly, until it boils. Boil two minutes until thick and clear, like pudding.
2. Separate the yolks and whites. Beat the whites until stiff. Add to the sugar mixture slowly, one spoon at a time, and mix. Add baking powder. Set aside.
3. In a bowl, mix cheese and yogurt. Add 4 of the egg yolks, discarding 2 yolks. * Pour the cheese mixture into the whites and fold in gently. Pour into 10" (26cm) spring-form pan.
4. Place in bottom third of the oven a pan with about 3/4" (2cm) of water. Preheat oven to 350F (180C).
5. Place spring-form pan in the warm water and cook for exactly one hour. Turn off the oven and leave in for 20 minutes with door slightly open.