Preheat oven to 375°. In a medium bowl, combine crushed pecans, goat cheese, salt, and pepper. Set aside.
Put the chicken breasts onto a baking sheet that has been oiled with olive oil. Brush the chicken breasts with dijon mustard. Press the pecan/goat cheese mixture onto the top of the chicken breasts. Bake for 40-45 minutes, until the chicken is cooked through.