Bring a large pot of salted water to a boil. Meanwhile, melt the butter in a large skillet over medium-high heat. Add the asparagus, peas, green beans, spring onions, yellow onion and a pinch of salt. Cook just until the onions soften, about 5 minutes. Add the heavy cream and chicken stock and cook until reduced slightly, about 3 minutes.
Meanwhile, add the pasta to the boiling water and cook as the label directs. Drain the pasta and transfer to the sauce; toss gently. Transfer everything to a serving bowl. Garnish with the parmesan and basil.
Photograph by David Malosh