Cook the pasta al dente as directed on the box; drain well but don't rinse; reserve about ¼ cup of the pasta cooking liquid; place the drained pasta back in the pot you cooked it in; set it aside.
Peel and devein the shrimp if necessary. Rinse the shrimp in cold water. Pat dry with a paper towel; place them in a bowl and mix in a couple of teaspoons of creole seasoning. Set aside.
Chop the onion into crescents; chop the garlic, slice the mushrooms, put the creole seasoning, kosher salt and ground black pepper in a little bowl, cut the butter and measure the cream. Open the can of diced tomatoes and let them drain through a large strainer. See Notes for fresh tomatoes.
Heat the oil and 2 tablespoons of butter in a large skillet over medium-high heat. When the oil/butter mixture is bubbling, add the sliced onions and sauté for a couple of minutes.
Add the mushrooms and continue to sauté until the mushrooms start to brown-about 5 minutes.
When the mushrooms are starting to brown and the onions are starting to caramelize, add in the garlic, Creole seasoning, kosher salt and black pepper. Continue to sauté until you can start to smell the aromatics of the garlic-about a minute or two.
Stir in the drained diced tomatoes and mix together well. Sauté another 2 or 3 minutes, stirring often.
Increase the heat to high and add the shrimp. Toss and stir together and sauté until the shrimp just start to turn pink-about 2 minutes.
Maintaining a high heat, add the remaining 2 tablespoons of butter to the pan.
Add the heavy cream, mix well and bring to a heavy simmer. Turn the heat down to a low simmer and let it thicken for about 3 minutes. (Keep an eye on it at this point-you don't want it to cook down and thicken so much that it won't be enough left to coat all the pasta, so you want it pretty juicy).
While the sauce is simmering, add the reserved ¼ cup of pasta cooking liquid to the cooked pasta and mix well.
Mix the pasta into the sauce, starting with about half. Once that is fully incorporated, add more pasta until it's the consistency you want. It should be creamy with all the pasta well coated with sauce.
Remove the skillet from the heat. Taste for seasoning and add more if desired.
Serve it with a sprinkle of grated Parmesan or Romano cheese on top.
Notes
When buying fresh shrimp with shells on, you will need to buy more than the quantity you need for the recipe to account for the weight of the shells. For shrimp with shells and heads on, buy about 1 ¾ to 2 pounds to net 1 pound of meat. If you find shrimp without the heads, buy about 1 ½ pound to account for the shells. Save the shells and heads to make Homemade Shrimp Stock for use in other recipes. The shells and heads can be frozen in airtight containers until you have enough to make stock.Substitutes for the shrimp are white meat chicken, cut into small cubes, or crawfish. If using crawfish tails, cook according to these same instructions. Chicken should be sauteed about 10 minutes before adding the cream for the sauce, then simmer an additional 10 minutes in the sauce.Use canned or fresh tomatoes. Drain canned tomatoes. For fresh, peel, de-seed and chop the tomatoes before adding. I use Bow-tie Pasta (commonly referred to as farfalle). Feel free to use your favorite shape. I recommend something broad or with ridges that will collect sauce like fusilli, penne or fettuccine just to name a few. Cook it al dente so that it does not overcook in the sauce.Leftovers can be stored in the fridge for 3 to 4 days in an airtight container. You can reheat in the microwave or in a saucepan on top of the stove. Make sure to stir it a couple of times while reheating so that the sauce does not separate.This can also be kept in the freezer. If it’s in an airtight container, it should maintain its quality for up to 6 months. Let it thaw in the refrigerator overnight, then reheat in the microwave or stovetop, stirring a few times so the sauce doesn’t separate. This goes well with a Sensation Salad. Some great side dishes with this are Sweet & Savory Green Beans, Yellow Squash Casserole or Roasted Asparagus.