2 tablespoons snipped fresh Italian parsley (optional)
Season chicken with salt and pepper. In a large nonstick skillet, brown chicken in hot butter or olive oil over medium heat for 2 minutes on each side. Remove from skillet; add mushrooms, leeks, and shallot. Cook and stir until mushrooms are tender. Return chicken to skillet; add ½ cup of the broth, Worcestershire sauce, and artichoke hearts. Bring to boiling; reduce heat. Simmer, covered, 10 minutes or until no pink remains in chicken (170°F).
Meanwhile, combine sour cream, flour, mustard, and remaining ¼ cup chicken broth in a bowl. Remove chicken and vegetables to serving platter with a slotted spoon; cover and keep warm. Stir sour cream mixture into skillet; cook and stir until thickened and bubbly. Cook and stir 1 minute more. Spoon sauce over chicken. Sprinkle with tomato and, if desired, parsley.