Cook farfalle according to package directions for al dente, adding 2 tbsp kosher salt to the pasta cooking water. Drain.
Meanwhile, preheat large pan on medium heat. Add olive oil, onions, mushrooms, salt, pepper and garlic powder. Stir, cook 10-12 min on medium to medium-high heat, stirring periodically until water from mushrooms evaporate and they start browning.
Add butter, stir to melt it, then add flour and stir. Drizzle in milk, stirring to combine. Bring to a low simmer and cook 3 to 5 minutes, avoiding the milk boiling. Slowly add cheeses, stirring frequently until cheese melts.
Stir in spinach and meatless crumbles until spinach starts to wilt. Stir in farfalle and parsley. Serve topped with optional toasted breadcrumbs.
