Pecan Chicken with Dijon Mustard Sauce

1 stick (1/2 cup) + 1 tablespoon butter, divided
4 tablespoons Dijon mustard, divided
6 chicken boneless, skinless chicken breast halves
8 ounces pecan, finely chopped
2/3 cup cour cream

Melt 1 stick butter in saucepan.  Turn off heat and stir in 3 tablespoons Dijon mustard until will blended.  Dip breast into mixture, then coat with chopped pecans.  Place in a 9x13 dish and bake at 450 degrees for 10 minutes; reduce heat to 350 degrees and continue baking 20 minutes more.  Just before serving, prepare sauce by heating remaining 1 tablespoon butter in a pan until melted.  Stir in sour cream and remaining 1 tablespoon Dijon mustard and immediately turn off heat.  Place a dollop of sauce on top of each breast and garnish with a pecan, if desired.