In a large skillet, heat oil over medium-high heat; brown meat in batches.
Transfer meat to a slow-cooker along with the onions, carrots, and bay leaves.
In the same skillet, add tomato paste, garlic, Italian seasonings, salt, pepper, and pepper flakes.
Cook and stir over medium heat until fragrant and slightly darkened, 2-4 minutes.
Stir in the mushroom powder, wine, and diced tomatoes until blended.
Transfer mixture to slow cooker; cover.
Cook on low until beef is tender, 7-9 hours.
Discard bay leaves.
Cook pasta according to package directions for al dente.
Serve ragu over pasta with Parmesan.