Peel, devein, and rinse the shrimp, pat dry with paper towels, and mix in 1 Tablespoon of Creole seasoning-then set aside in a bowl. Slice sausage into medallions, chop shallots, garlic, and green onions. Measure butter, stock, heavy cream, lemon juice, and Creole seasoning. Set aside. Cook pasta according to the instructions on the box. Set aside. Reserve 1 cup of the pasta's boiling liquid.
To begin, sauté the sausage in the olive oil over medium high heat for about 3 minutes. Remove the sausage from the pan and set aside.
Add the shrimp and saute for about 2 minutes, total. Turn the shrimp over once to make sure you catch both sides. Remove the shrimp from the pan and set aside. Leave the oil and browned bits of sausage and seasoning in the pan.
Next, add the butter. When the butter is melted and starting to bubble, add the shallots; sauté for 1 or 2 minutes.
Add the the garlic and stir until just aromatic, about 1minute. Add about half the Creole seasoning, mix well.
Deglaze the pan with a little chicken stock, scraping all the browned bits off the bottom. Add the remaining chicken stock and mix well.
Add the lemon juice. Mix well and bring to a low boil before lowering the heat. Simmer with the pan uncovered for about 3 to 5 minutes, allowing the stock to reduce slightly.
Add the heavy cream and mix well. Increase the fire and bring everything to a boil, then lower the heat to maintain a slight simmer. Stir in the green onions; maintain the simmer for about 2 minutes then stir in the Creole mustard, starting with about half. Taste and add more if needed.
Add back the sausage and stir to combined. Simmer for 2 minutes,
Add back the shrimp and the remaining Creole seasoning and salt and pepper. Mix well, cover and simmer about 2 minutes.
Now is the time to add in the cooked pasta. Start with about half of the pasta and ¼ cup of pasta water and mix thoroughly. Add more pasta and a little pasta water (¼ cup at a time) as needed to get the consistency you want. Don't add so much that the sauce doesn't coat all the pasta. It should be creamy, all the pasta should be coated with the sauce; you may not use all of the pasta.
Remove from the heat and let sit for about 5 minutes, then serve.
Notes
Read my article Shrimp and Andouille Pasta in Creole Mustard Sauce, for greater detail and Tips with step-by-step photos.This is also great with chicken in place of shrimp. Check out the recipe for Pasta David.Leftovers can be stored in the fridge for up to 5 days in an airtight container. To reheat, use the microwave or slowly warm in a saucepan over low heat, stirring often. I do not recommend freezing leftover pasta in cream sauce.When adding in the cooked pasta, start with half and mix it all. Add more as needed, but you want the finished product to be very creamy, so don't overdo the pasta.Most commercial Creole seasoning contains salt, so keep that in mind when using it. This recipe was developed with salt-free Creole seasoning, so you may not need as much salt depending on your Creole seasoning.