For the vanilla soufflé melt butter and grease the soufflé molds. Then put a tablespoon of sugar into the first mold and rotate so that the sugar will adhere to the bottom and sides of the mold and pour the excessive sugar into the next mold. Repeat until all molds are greased with butter and covered with sugar. Preheat the oven to 200°C (top/bottom heat). Separate eggs and beat egg whites with a pinch of salt until stiff. Put aside. Put yolks, sugar, vanilla seed and grated lemon zest in another bowl and whisk with the electric mixer until frothy. Add ricotta and mix in with the whisk. Then fold in beaten egg whites and sieved cornstarch.