Slice the boneless skinless chicken breasts thinly and pat them dry with paper towels. Toss the chicken pieces in olive oil and blackened seasoning until evenly coated. Allow to marinate at room temperature for 15-30 minutes.

Bring a large pot of salted water to a rolling boil, then add the fettuccini noodles. Cook for 10-12 minutes, or until al dente. Reserve 2-3 cups of pasta water before draining.

In a large skillet, heat a tablespoon of olive oil over high heat. Add the marinated chicken and cook undisturbed for 4-6 minutes per side until browned and cooked through (internal temperature should be 160-165°F).

In the same skillet, reduce heat to medium and melt a couple of tablespoons of butter. Add shallots and sauté for 2-3 minutes. Add minced garlic and cook for an additional 30 seconds.

Deglaze the skillet with about a cup of reserved pasta water, scraping up any bits stuck to the pan. Stir in the heavy cream and let simmer for 2-3 minutes to thicken.

Add drained fettuccini to the skillet, tossing to coat in the creamy sauce. Gradually add more reserved pasta water if the sauce is too thick. Cook for an additional 1-2 minutes.

Remove from heat and stir in freshly grated Parmesan cheese until melted. Adjust seasoning with salt and pepper as needed.

Slice the seared chicken into strips and lay them over the creamy fettuccini before serving. Garnish with extra Parmesan and black pepper, if desired.