To begin, slice each chicken breast through the center to create two thinner fillets. Cover them with plastic wrap and use a meat mallet or the side of a can to pound them to an even thickness, about ½-inch thick. This will ensure that the chicken cooks evenly and stays tender. Once the chicken is ready, mix all the blackening seasonings in a small bowl. Use this seasoning mixture to generously coat both sides of the chicken. Let the seasoned chicken rest while you prepare the pasta and sauce.
Bring a large pot of heavily salted water to a boil. Cook the fettuccine just until al dente, which should take about 8-10 minutes. Reserve ½ cup of the pasta water before draining the pasta. Once drained, toss the pasta with a drizzle of olive oil to prevent it from sticking together and set it aside for later use.
In a large, heavy-bottomed skillet, heat 2 tablespoons of butter and 2 tablespoons of olive oil over medium-high heat. Once the pan is hot, add the seasoned chicken fillets and cook for about 4-5 minutes on each side, or until golden brown and fully cooked through. Remove the chicken from the skillet and place it on a cutting board. Loosely cover it with foil and let it rest for at least 5 minutes before slicing or chopping it into bite-sized pieces.
In the same skillet where you cooked the chicken (don’t wipe it out), melt the remaining 2 tablespoons of butter over medium-low heat. Add the minced garlic and the remaining tablespoon of blackening seasoning, cooking for about 3 minutes until fragrant. Pour in half of the chicken broth and whisk the remaining broth with the cornstarch until smooth. Add this mixture into the skillet along with the heavy cream. Bring the sauce to a simmer and let it thicken, stirring occasionally. Once the sauce has thickened to your desired consistency, reduce the heat to low and stir in the freshly grated Parmesan cheese until melted and creamy.
Add the cooked fettuccine into the skillet with the Alfredo sauce and toss everything together to coat the pasta evenly in the sauce. If needed, add a little reserved pasta water to adjust the sauce’s consistency. Then, slice the rested chicken and add it to the skillet, along with any juices that have accumulated on the cutting board. Taste the dish and adjust the seasoning with additional salt, pepper, or cayenne for extra spice. Garnish with fresh parsley and serve immediately.