Slice the white part of the leek into thin strips and add to a frying pan with butter in it. Saute the leek for about 3 minutes then add the chopped garlic. Fry until the garlic is golden brown. In a large cassarole dish lay the 4 chicken breast side by side.Combine the rest of the ingredients in a large bowl and mix with a large spoon. Add the sauted leek and garlic to the bowl. Once mixed pour entire contents of bowl over chicken Bake at 350 for 35-45 minutes. Serve over rice or mashed potatoes and enjoy.