Add 1 of the 2 boneless skinless chicken breasts to a cutting board. Hold your knife parallel to the board and carefully slice the chicken from right to left (if you’re a righty)… opening the chicken breast up like a book. Slice all the way through, so you now have 2 thinly sliced pieces of chicken. Repeat with other chicken breast.
Here's a link to a good tutorial for doing this, although I typically don't pound the chicken. https://www.seriouseats.com/knife-skills-how-to-cut-chicken-breasts-into-cutlets
In a small bowl, combine the 1 tsp kosher salt, 1 tsp italian seasoning, 1/2 tsp garlic powder, 1/2 tsp onion powder, and 1/2 tsp black pepper.
Season chicken on both sides.
Cook chicken
Heat a large skillet over MED heat. Once hot, add 2 Tbsp olive oil, and the seasoned chicken and cook until cooked through and golden brown, about 4 minutes per side.
Remove cooked chicken to a plate and set aside.
Make sauce
Add 3 Tbsp unsalted butter to the same skillet, and once melted, add 2 shallots, and 3 cloves garlic. Cook 3-4 minutes, until softened.
Add 2 Tbsp all purpose flour, and stir to combine. Cook for another minute.
Cooking the flour is important to do, otherwise the sauce will taste like raw flour.
As you whisk/stir, pour in 1 2/3 cup reduced sodium chicken broth. Once mixed in, with no lumps of flour, add 3/4 cup heavy cream, 3 Tbsp dijon mustard, and 2 tsp Worcestershire sauce. Whisk/stir to combine well.
Bring sauce to a simmer, and cook for several minutes, or until the sauce thickens a bit.
Stir in 1/2 cup grated Parmesan cheese, until melted.
Finish and serve
Return the chicken to the pan, nestling into the sauce. Cook for a minute or two, to heat the chicken through.
Sprinkle with minced fresh parsley (if using), and serve hot. I like to serve this chicken with some mashed potatoes, rice, or noodles, and a vegetable.
Notes
I've estimated this recipe serves 4, but the exact serving size and number of servings is up to you.
Instead of slicing the chicken breasts in half, you could purchase thin cut chicken, or chicken cutlets from the store.