Pasta all'ortolana

This variation is from Diane Henry's Simple cookbook.  I made it with four summer squash, almost equal to the amount of noodles and it was very popular.

• Salt
• 10 oz. spaghetti
• 2 tablespoons extra virgin olive oil
• 1 teaspoon butter
• 1 yellow onion, chopped
• 3 cloves garlic, minced
• 3-4 summer squash, yielding 4 cups baton shaped
• Salt and pepper
• 4 egg yolks, 2 whole eggs
• 1 cup grated Parmesan cheese (plus more for topping)
• 1 teaspoon lemon zest
• 1/2 cup basil leaves, sliced thin

Add the pasta to the boiling water to cook: Add pasta to boiling salted water. The pasta should take about 10-12 minutes to cook until al dente (cooked but still a bit firm), which is just about the right amount of time you'll need to cook the vegetables. Cook with a rolling boil, uncovered. 4 Sauté onions, garlic, summer squash: While the pasta is cooking, add the onions, garlic, and summer squash. The heat should be medium high.
Stir the vegetables so that they are all coated with oil from the pan, then spread them out in the pan, generously salt and pepper them. Cook until they are just lightly browned, stirring only occasionally. Remove from heat.

5 Beat the eggs, add Parmesan and lemon zest: In a medium bowl, beat the eggs and mix in the grated Parmesan and lemon zest.

6 Add cooked pasta to vegetables, stir in egg mixture: When the pasta is ready, reserve 1/2 cup of the cooking liquid, then drain the pasta. Add the pasta to the squash and onions (or add the veggies to the pasta, depending on the size of your pans).
Pour the egg, Parmesan, lemon zest mixture over the pasta mixture and quickly stir in with a wooden spoon. The heat from the pasta will sufficiently cook the eggs.

Add a little of the reserved pasta cooking water if it looks a little dry. Stir in the prosciutto and basil.