Bring a pot of salted water to a boil. Cook the ditalini until just al dente according to the package directions. Reserve 1 cup pasta water, then drain.
Meanwhile, heat the olive oil and 1 tablespoon vegan butter in a large skillet over medium-high heat. Add the mushrooms and cook 6–8 minutes, until well browned.
Reduce to medium. Add the remaining 1 tablespoon butter, garlic, and thyme then cook for 30–60 seconds. Sprinkle in the flour and stir for about 1 minute.
Slowly stir in the vegetable broth, followed by the vegan cream. Simmer for 2–3 minutes until slightly thickened.
Add the Parmesan, salt, and pepper. Stir in the cooked ditalini and enough reserved pasta water to make everything loose and creamy. Cook together for another 1–2 minutes.
Remove from the heat and stir in the lemon juice. Taste and adjust seasoning. Garnish with parsley and serve.