Season both sides of the chicken with salt and pepper. If using breast, slice each breast horizontally into 2 thin steaks and pound to 1/2 inch even thickness.

Heat the olive oil in a large cast iron or stainless steel skillet (not non-stick) over medium-high heat. Place chicken smooth side-down and cook for 4 minutes until deeply golden. Flip and cook another 3 to 4 minutes until the internal temperature reaches 162 degrees F (72 degrees C). For breast: cook on high heat for 2 minutes per side, targeting 153 degrees F (67 degrees C). Remove chicken to a plate to rest.

Scrape out and discard any loose burnt bits from the pan, leaving the golden fond behind.

Return the pan to medium heat. Add the cream, Dijon mustard, and wholegrain mustard. Stir with a wooden spoon, scraping up the fond from the bottom of the pan, until the mustard is fully dissolved and the sauce is hot but not simmering.

Stir in the salt, pepper, and fresh herbs if using. If the sauce is too thick, add water one tablespoon at a time until you reach your desired consistency.

Place the chicken on serving plates and spoon the sauce generously over the top. Serve immediately.