Step 1: Prepare the Chicken

1. Pat the chicken breasts dry with paper towels.
2. In a small bowl, mix together the Cajun seasoning, smoked paprika, garlic powder, onion powder, dried oregano, salt, and black pepper.
3. Rub the seasoning mixture evenly over both sides of the chicken breasts, pressing it into the meat for maximum flavor.

Step 2: Cook the Chicken

1. Heat a large skillet over medium-high heat. Add the olive oil and butter.
2. Once the butter is melted and sizzling, place the seasoned chicken breasts in the skillet.
3. Cook for 4-5 minutes per side, or until the chicken is golden brown and fully cooked (internal temperature should reach 165°F or 74°C).
4. Remove the chicken from the skillet and set it aside on a plate, tented with foil to keep warm.

Step 3: Prepare the Mustard Cream Sauce

1. In the same skillet, reduce the heat to medium and add the butter.
2. Add the minced garlic and sauté for about 30 seconds, until fragrant.
3. Stir in the Cajun seasoning and let it toast for a few seconds to release its aroma.
4. Pour in the chicken broth and scrape up any browned bits from the bottom of the pan. Let it simmer for 1 minute.
5. Reduce the heat to low and stir in the Dijon mustard, whole grain mustard (if using), Worcestershire sauce, and honey.
6. Slowly add the heavy cream while stirring continuously.
7. Simmer the sauce for 3-4 minutes, then stir in the Parmesan cheese and cayenne pepper (if using).
8. Let the sauce thicken slightly, then season with salt and pepper to taste.

Step 4: Combine and Serve

1. Return the cooked chicken breasts to the skillet, spooning some of the sauce over the top.
2. Simmer for 1-2 minutes until the chicken is warmed through and coated with the sauce.
3. Garnish with chopped parsley and red pepper flakes.