Mix the ricotta with 100 g sugar, cinnamon, chopped walnuts and 2 eggs. Quarter, peel and core the apples and cut into very fine cubes. Add to the ricotta.
Fill the ricotta mixture into the cannelloni with a piping bag or freezer bag (cut a hole in the corner) and place in a buttered casserole dish.
Finely grate the marzipan, mix with the milk, the remaining eggs and sugar. Pour over the cannelloni and cover the pan with aluminum foil. Bake in the preheated oven with top and bottom heat 200 degrees (convection 180 degrees) on the middle rack for 40 minutes.
Remove the foil 15 minutes before the end of the cooking time so that the surface browns slightly or turns golden yellow if desired.
Cranberry jelly or a fruity sauce go well with it.
My guests are always enthusiastic about this dessert, usually double the amount. The children in particular are impressed and call ahead of an invitation to request this dessert! My niece (10 years old) wants this as a warm main course every now and then and even likes the cannelloni when it`s hot outside, cold from the fridge (which is the exception, however). Is really very tasty.