Season the chicken on both sides with the salt, and white pepper. Heat the olive oil in a 12-inch saute pan over medium-high heat. Place the chicken in the pan, and cook until golden, about 4 minutes per side.
Increase the heat to high, add the shallot, garlic, white wine, salt, and pepper, to taste, and continue to cook until the chicken is just cooked through, about 4 minutes. Remove the chicken breasts and set aside.
Add the chicken broth and whisk in the mustard and double cream (or yoghurt) into the pan, and bring the sauce to a gentle simmer. Cook 2 minutes, until thickened and bubbly.
Add the tarragon and parsley, and remove from the heat. Spoon the sauce over the chicken, and serve immediately.