Gather and prep the vegetables. Slice off the white or purple base of the onion, and mince. Reserve minced onion in a small bowl. Cut the stalk into very thin strips.

Bring a large pot of salted water to a boil. Add fettuccine and cook to al dente. (Fettuccine sticks together easily, so give the boiling water a few swirls as pasta cooks.) Reserve a cup of pasta cooking water for plating.

Meanwhile, set a large, deep-sided skillet over medium heat. Cut off a tablespoon of butter and divide into thirds. Add one third to the pan and when bubbly and fragrant, toss in carrots. Sprinkle carrots with a tiny pinch of sea salt and a squeeze of lemon juice. Sauté until carrots are just soft, but still have a bit of bite in the middle, 2 - 3 minutes. Remove cooked carrots to a bowl. Add another third of butter, followed by chopped asparagus, sea salt, and a squeeze of lemon juice. Sauté just until tender, about 2 minutes. Remove to a bowl. Add the remaining third of butter, followed by spring onion and green garlic strips, a pinch of sea salt, and a squeeze of lemon juice. Sauté 2 minutes and then remove to a bowl.

Deglaze pan with 1 tablespoon dry vermouth and then stir in remaining 2 tablespoons butter. Add reserved minced onion and sauté until golden, about 2 minutes. Turn heat to low, and stir in heavy cream followed by Parmesan. Fold in most of the fresh herbs, reserving some for garnish. Taste sauce, and add lemon, a splash of vermouth, or sea salt as needed. Gently fold fettuccine into the sauce and add kale ribbons, followed by cooked vegetables. If mixture gets at all sticky, add a splash of pasta cooking liquid to loosen the noodles.

With a large serving fork, twirl fettuccine into shallow bowls, finish with reserved herbs, pepper, and Parmesan shavings. Serve immediately.