Add the flour to a bowl; then coat each piece of chicken on both sides and place on a dish; repeat for all. Heat the oil over medium high heat in a large nonstick skillet.

When the oil is hot, add the chicken and cook 2-3 minutes per side until the chicken is lightly brown on both sides and almost cooked through. Remove the chicken from the pan, place on clean dish and allow to rest while you make the sauce.

Next, add the butter to the pan, allow to melt; then add the garlic and rosemary. Cook for 1 minute; then add 1 tablespoon of flour and mix to form a roux.

Add the chicken stock, mustard, heavy cream, salt and pepper to the pan, mix well; then add the chicken back to the pan.

Reduce heat to low, cover the pan and cook for an additional 5-8 minutes until the chicken is cooked through and the sauce is creamy. Remove from the pan, place on a serving platter and serve.