Preheat oven to 350°F
In bowl mix together yogurt and mustard.
Sprinkle chicken lightly with mustard mixture in a small bowl.
Spread mixture on both sides of chicken.
Place in baking pan.
Combine bread crumbs, thyme, salt and pepper and sprinkle over chicken.
Bake for 30 to 35 minutes until golden-brown and no longer pink in the center