1Use a 2-cup pyrex to measure out 1 1/2 to 1 3/4 cups of mixed pasta; break about 1 ounce of long spaghetti in halves or thirds; place in the cup, and add enough of the rotini (about 2 ounces) to make up the difference.
2Cook pastas together; spaghetti will be over-cooked, and the starch will act as a binder.
3While the pasta is cooking, brown beef; remove fat as it appears.
4When meat is no longer pink, then add olive oil and onions and fry, stirring, to soften and sweat the onions.
5Add garlic, mushrooms, parsley, and the Italian seasoning and blend.
6Continue cooking and stirring until mushrooms are warmed (not limp).
7Remove from heat but keep warm.
8Drain the pasta but do not rinse.
9Put pasta back in the pot used to cook it.
10Add the hamburger mixture.
11Make a well in the center of the spaghetti mixture and working quickly, mix the egg and extra oil.
12Using moderately high heat, quickly pour the egg mixture into the well and stir, constantly, to both coat the pasta, and to cook the egg.