Bring a medium saucepan of salted water to the boil. Add pasta, then reduce to a simmer for 6 minutes. After 6 minutes, add asparagus and peas and continue to simmer until pasta is al dente, around 4 minutes more.
Meanwhile, heat the olive oil in a large pan over a medium heat. Add garlic and onion and sautee until softened, 2-3 minutes. Then add mushrooms and cook for a further 5 minutes.
Add butter to the pan. Stir until just melted, then add the white wine. Stir and bring to a simmer, then leave to reduce for 7-8 minutes.
Dissolve cornstarch in warmed oat milk and stir until there are no lumps. Once the wine has reduced by half, slowly add the cornstarch mixture to the pan, and stir continuously until sauce is thick and creamy.
Drain the pasta and vegetables, and add to the pan with the sauce. Stir to coat and warm through. Season to taste with salt and pepper. Serve immediately.
*Use whichever pasta shape you fancy. I used rigatoni here as it holds the sauce really well, but spaghetti or penne would also work great.