In a medium bowl, toss the shrimp and creole seasoning together until well combined. Set aside and allow to rest.
In a large pot over medium-heat, add in oil. Once hot, add the sausages and cook for 3-5 minutes, or until lightly browned. Transfer sausages to a bowl, leaving any drippings behind in the pot and set aside.
In the same pot, add in the onion, bell pepper, mushrooms, and garlic. Cook for 5-7 minutes or until the onion is translucent and veggies are tender.
Add in the butter and lemon juice. Stir for 1 minute.
Reduce heat to medium-low.
Stir in the tomato paste and flour. Continue to mix and cook for 1 more minute.
Stir in the stock (or water if using), heavy cream, and pasta.
Cover the pot with a lid and cook for 10-12 minutes.
After 10-12 minutes, uncover the pot and add in the cooked sausages and shrimp. Cook uncovered for 5-7 minutes.
Remove the pot from the heat, cover the pot once more, and let rest for 10 minutes. No peeking!
After the last 10 minutes, stir in the red pepper flakes (is using) and grated parmesan cheese. Season with salt and pepper.
Serve with bread or your choice of sides.
