In a large skillet heat the olive oil to medium high heat.
Saute the chicken breasts about 4-5 minutes per side or untl cooked through and lightly golden. Remove from skillet and slice into thick slices about 3/4 inch thick. . Do not wipe out the skillet.
Add the shallot to the skillet and saute until cooked, about 3 to 4 minutes then add the white wine and scrape up all the small pieces from the bottom of the skillet. Simmer for about 2 minutes then reduce by half.
Add the chicken stock and continue to simmer for about 4 minutes. Add the mustard, cream and butter.
Plate up the chicken slices and pour the mustard sauce over then add a good handful of Arugula on the side and serve.