1Drop the pasta into boiling water to cook while you make the sauce.
2Melt half the butter and all of the olive oil in a skillet. Add the onion, garlic, and zucchini. (If you’re using dried herbs instead of fresh, add them now.) Saute until the onion is translucent and the zucchini is soft.
3Add the peas, prosciutto, sage, and rosemary; saute for another minute or two.
4Turn the heat down to medium low and stir in the flour and milk mixture a little at a time. Cook, stirring constantly, for about 30 seconds. Add the parsley and cook, stirring, for another 30 seconds.
5Off the heat, swirl in the remaining butter. Quickly mix in the egg yolk and the grated cheese. Taste and correct for salt.
6When the pasta is cooked, drain it and toss in a serving bowl with the sauce. Serve hot.
7*You can use dried pasta from a box, or make your own fresh pasta with finely ground sage & rosemary mixed into the dough. If you do that (worth the extra work, in my opinion), use slightly less herbs in the sauce.
Creamy and springy, Julia's Pasta Bake is a brunch favorite! Make-ahead: prepare the first two steps in advance and refrigerate until ready to bake. Prepare topping and bake until golden. See more spring recipes here.