Prep the chicken. Slice the chicken breasts in half so they cook evenly. Mix all of the Blackening seasonings together in a small bowl.
Season both sides of the chicken with the seasonings, if there is some leftover, use it in the alfredo sauce later! Let the chicken rest to the side while you prep the rest of the ingredients and get the pasta started.
Cook the pasta. Heavily salt the water, add the fettuccini and cook until al dente (follow the instructions on the box). Once the pasta is cooked be sure to save some pasta water to thin the Alfredo sauce.
Cook the blackened chicken. While the pasta is cooking. Melt 1 tablespoons butter in 1 tablespoons oil in a large skillet over medium-high heat. Once hot, add chicken and cook for 5-7 minutes per side until golden/blackened and cooked through (165º internally)
Once the chicken is cooked through, add it to a clean cutting board to rest. Do not wipe the pan clean! This is extra flavor for the sauce.
Make the alfredo sauce. Melt 1 tbsp butter in the same pan with the chicken drippings, add remaining olive oil and garlic. Let it simmer for a minute. Add in the broth and cornstarch, bring to a simmer. If you have any leftover seasonings feel free to add a pinch to the sauce for an extra kick. Whisk often and let it simmer for about 3-5 minutes or until it thickens a tad bit. Turn the heat down to low on the skillet. Add the milk and parmesan, fold in the cooked pasta. If needed, add some pasta water to the skillet to help thin the sauce a bit. Continue to simmer until the parmesan is melted.
Slice the chicken, add it to the skillet and serve. Feel free to add more parmesan and garnish with some fresh basil or parsley.