Start by bringing a large pot of salted water to a boil. Add the fettuccine pasta and cook according to package instructions until al dente. Drain the pasta and set aside.
In a large skillet, heat 3 tablespoons of olive oil over medium heat. Add the diced onion and sauté for about 3-4 minutes until translucent. Stir in the minced garlic and cook for an additional minute until fragrant.
Next, add the sliced mushrooms to the skillet. Cook for about 5-7 minutes, stirring frequently, until the mushrooms are tender and have released their moisture.
Add the sliced roasted peppers and calamari rings to the skillet. Stir everything together and cook for about 3-4 minutes, or until the calamari is opaque and cooked through.
Pour in the half-and-half or heavy cream, stirring to combine. Season the mixture with dried Italian herbs, pepper, red pepper flakes (if using), and salt to taste. Allow the sauce to simmer for about 3-5 minutes, letting it thicken slightly.
Add the cooked fettuccine to the skillet, tossing it gently in the creamy sauce until well-coated. If needed, you can add a splash of pasta water to help loosen the sauce.
Once everything is well combined, remove the skillet from heat. Serve the Creamy Calamari Fettuccine hot, garnishing with freshly chopped parsley for a pop of color and freshness.
