Bring a large pot of salted water to a boil. Cook the pasta according to the package instructions until al dente. Before draining, reserve 100ml of pasta water.
Sauté the Mushrooms
Meanwhile, heat the olive oil and plant butter in a large frying pan over medium-high heat. Add the mushrooms in an even layer and cook for 6-8 minutes until golden brown and lightly caramelized.
Add Garlic and Sage
Reduce the heat slightly and stir in the garlic and chopped sage. Cook for 1 minute until fragrant.
Make the Sauce
Pour in the oat cream and bring to a gentle simmer.
Stir in the white miso paste, soy sauce and nutritional yeast and season with salt and black pepper. Add a splash of the reserved pasta water to loosen the sauce if needed.
Combine
Add the drained pasta to the frying pan and toss well until every strand is coated in the creamy mushroom sauce. Stir in more pasta water as necessary to create a silky consistency.
Serve
Divide among bowls and top with chopped fresh parsley, and a few crispy sage leaves if desired.