Finely chop the onion and fry in a small amount of vegetable oil with mushrooms.
Walnuts chop or grind not very large, but not in the dust. Assemble the salad in layers.
1) ham, smear with mayonnaise
2) mushrooms with onions
3) egg, smear with mayonnaise
4) walnut
5) cheese, grated on a fine grater