Bring a large pot of salted water to a rolling boil. Add the short pasta and cook according to package instructions for about 8-10 minutes until al dente. Drain and reserve some pasta water.

In a large skillet over medium heat, add olive oil. Once shimmering, add chopped onion and sauté for 2-3 minutes until translucent and fragrant.

Add sliced mushrooms to the skillet and stir frequently for about 3 minutes until browned. Transfer them to the bowl with the onions.

In the same skillet, add more olive oil if needed and toss in the fresh spinach. Sauté for 2 minutes until wilted and vibrant green. Set aside with mushrooms and onions.

Reduce heat to medium-low, add minced garlic, and cook for about 30 seconds. Pour in vegetable broth and stir in heavy cream, grated parmesan, chili flakes, and Italian seasoning. Cook 2-3 minutes until smooth.

Return the cooked pasta, mushrooms, onion, and spinach to the skillet and toss to combine. Add reserved pasta water as needed to achieve desired sauce consistency. Cook for an additional 1-2 minutes.

Remove from heat, plate the garlic parmesan pasta, and sprinkle with additional parmesan and chili flakes if desired. Serve warm.