Start by pounding the chicken breasts to an even thickness. Season both sides generously with the blackening seasoning.
In a large skillet, heat the olive oil over medium-high heat. Add the seasoned chicken breasts and cook for about 5-7 minutes on each side until cooked through. Remove from skillet and let rest.
In the same skillet, reduce heat to medium and add the butter. Once melted, add the minced garlic and sliced red bell pepper, sauté for 2-3 minutes until fragrant.
Slowly pour in the heavy cream, stirring to combine. Add cream cheese and whisk until melted. Stir in Parmesan cheese, salt, black pepper, white pepper, and thyme, cooking until sauce thickens.
Add the cooked fettuccine to the skillet, tossing to coat evenly with the sauce. Fold in sliced blackened chicken and heat through.
Serve hot, garnished with additional Parmesan cheese if desired.