1.   The egg in the mixture makes it stay put, instead of running all over the place as most cheese mixtures do.

2.   Beat the egg yolk, and combine it with the cheese mixture to bind it.

3.   A handful at a time, stir cheese mixture into wine, stirring first batch until it is almost completely melted before adding another.

4.   Add the melted cheese mixture to potatoes and beat with electric mixer until fluffy.

5.   Add the remaining whites to the cheese mixture and gently fold until blended.

6.   Add to cooled cheese mixture.

7.   Add egg yolks to cheese mixture, one at a time, heating well after each.

8.   Alternately layer noodles, ricotta cheese mixture, mozzarella cheese and sauce, forming two layers.

9.   Continue with another thin layer of the cheese mixture and a layer of mushrooms.

10.   Cover with remaining noodles, spaghetti sauce, spinach and remaining Parmesan cheese mixture.