For Sauce
in a medium sauce pan over medium heat, melt butter. Add onion and cook until onion is starting to turn translucent. Add garlic and cook for an additional minute.
Add the flour and continue to cook for about 5 minutes or until the raw smell of flour dissipates and the mixture starts to turn into light brown color.
In the microwave, heat the milk until quite warm, but not simmering.
Remove the pan from the heat temporarily and slowly add the hot milk, stirring with a whisk to avoid clumps. Return to heat.
Add the garlic powder, salt, pepper and stir to combine. Return to a simmer.
In small handfuls, add the parmesan while constantly stirring. Wait about a minute between handfuls so the cheese can melt and get incorporated. Turn heat to very low, keeping the sauce warm until serving, stirring occasionally.
If making your own Blackened seasoning, stir all ingredients together in a small bowl.
For Chicken
Pat the chicken dry using paper towels.
Coat the chicken using oil or cooking spray. Sprinkle blackened seasoning on one side, making sure to coat liberally. Leave the other side of the chicken unseasoned for now. Reserve the remainder of the seasoning for other side later.
In a large saucepan over medium high heat, add the oil. and heat until just starting to smoke.
Carefully place the chicken into the pan with the seasoned side down. Season the top side of chicken with the remaining seasoning.
Cook for 5 to 7 minutes. flip and continue to cook adding a cooking weight if you have one.
Once internal temp of the chicken reaches 165° F, remove from heat and remove chicken onto a plate and cover with aluminum foil to keep the chicken warm until serving.
Keep the uncleaned pan available for later use.
For Pasta
In a large pot of water . . . well, I don’t feel like I need to explain how to cook pasta. Anyway, cook the pasta making sure to cook it until al dente and reserve a cup of the cooking water.
When cooked, drain the pasta and add to the pan you used for the chicken. Over medium high heat, Add about of cup of the pasta water to the pan. Add the alfredo sauce one ladle at a time, stirring until it reaches the desired consistency.
Bring the pasta to a simmer then remove from heat.
Slice the chicken and add it to the top of the pasta and serve. Add parmesan cheese for garnish.