Take a large and deep bowl for whipping, pour the cream into it. Add some of the powdered sugar to make the buttercream for the cake and start whipping with a mixer. Gradually pour in the rest of the powdered sugar and vanilla sugar. Continue whipping at low speed for 1 minute.
Increase the mixer speed to maximum and continue beating for 2-3 minutes until the buttercream doubles in volume. You should get a fluffy mixture that does not settle.
Cream with cream is ideal for soaking traditional sponge cakes. Cakes with such cream are tender and juicy. After combining the butter cream and cakes, put the dessert in the refrigerator to infuse.