Bring a large pot of water to a boil and cook the pasta according to the package instructions.

Meanwhile, finely dice the onion, slice the zucchini, and cut the broccoli into florets. Heat the olive oil in a large pan, add the onion, and sauté for about 2 minutes. Add the zucchini, broccoli, spinach, and peas, season with salt, and cook for another 2 minutes. Pour in ¼ cup of water, stir, cover, and let the vegetables simmer until tender.

Prepare the sauce. In a small bowl, combine the cream, egg yolk, grated cheese, salt, and pepper. Whisk with a fork until smooth.

Pour the sauce into the pan and cook, stirring, until it just begins to simmer. Add the cooked pasta and toss to combine. If the sauce is too thick, loosen it with a little of the reserved pasta cooking water.

Serve topped with extra grated cheese.