Blend the blackened seasoning mix in a resealable container.
Cook the pasta in salted water per the package directions. Drain in a colander; leave in the colander for now. Tip - while the pasta is cooking, go ahead and start on the next step.
Pat dry the chicken tenderloins with paper towels. Apply a generous sprinkle of blackened seasoning mix on both sides of the tenderloins. As a reference, I use 1 teaspoon of seasoning mix for all 8 tenderloins - but if you like it more spicy, use more seasoning mix.
In a large cast iron skillet, add 1 tablespoon of butter and 1 tablespoon of olive oil. Turn heat to medium-high. When the butter begins to melt, blend it with the olive oil. Add the tenderloins and cook 3-4 minutes per side or just until done. If the skillet looks dry after you've turned the chicken over, add another tablespoon of butter to the skillet. Note - the tenderloins should have a "blackened" look, but not burned. If they start to burn, turn the heat down just a bit.
When the chicken is cooked, remove the skillet from the heat. Transfer the chicken to a plate and cover it loosely to keep it warm.
Return the skillet to the heat and lower the heat to medium. Add 2 tablespoons of butter to the skillet and let it melt. Then add the cornstarch and blackened seasoning mix. Stir with a whisk until blended.
Add the milk to the skillet. Simmer at a gentle boil for 2-4 minutes or until it's thickened, stirring with a whisk occasionally.
Remove the skillet from the heat and stir in the parmesan cheese and then the cooked pasta.
Taste test the pasta alfredo and add more blackened seasoning or salt, if needed (I usually add about 1 teaspoon of salt at this point). Important - add salt a little at a time and keep testing until the flavor suits you.
For each serving, plate the pasta alfredo with 2 or 3 tenderloins on top of the pasta. Drizzle with some some additional sauce if desired, and sprinkle with a little parsley.