This is soooo good! and so easy to make! The chicken is tender and just a bit spicy (because of the Dijon mustard) and the sauce is a snap to make and very tasty.
Sprinkle chicken with salt and pepper; place in a greased 13x9" baking dish.
Combine butter and the 4 tablespoons of mustard; stir well. Pour over chicken; sprinkle pecans over top.
Bake, uncovered, at 375 for 35 minutes or until chicken is done.
Remove chicken to a serving platter, reserving drippings in dish; keep warm.
Combine remaining 1 tablespoons mustard, pan drippings, and sour cream in a large saucepan; cook over medium heat until thoroughly heated, stirring often.