Preheat the grill to medium heat. Set out a small bowl. Add the mayonnaise, mustard, paprika, 1/2 teaspoon salt, and 1/8 teaspoon ground black pepper. Mix until smooth.
Brush the mustard mixture on one side of each chicken breast. Place the chicken on the grill with the mustard side down. Then brush the tops with the mustard mixture.
Grill for 5 minutes per side, flipping once. Allow the chicken to cool for 5 minutes before serving.
Baked Magic Chicken: Don't have a grill? This recipe can be easily cooked in the oven. Preheat the oven to 350 degrees F. Place the chicken on a rimmed baking sheet lined with parchment paper. Brush both sides with the mustard mixture, then bake for approximately 20-25 minutes.