Cheese Stuffed Shells

• 20 pasta shells (jumbo)
• 1 container ricotta cheese
• 1 egg yolk
• 475 ml prepared spaghetti sauce
• 75 gr ham chopd (finely)
• 40 gr parmesan cheese (grated)
• 7 gr parsley (chopped)
• 1 gr oregano
• 1 gr salt
• 1 gr pepper