1/2 cup miso paste
4 Tbs. unsalted butter, room temperature
1 Tbs. apple cider vinegar
1 Tbs. sugar
2 (10- to 12-oz.) boneless, skinless chicken breasts
Preheat oven to 350°F.
Combine the miso, butter, vinegar, and sugar into a paste and rub it all over the chicken breasts. Let the chicken marinate in the paste for 10 minutes. This rest period will allow the chicken to come to room temperature, which in turn will help the chicken cook more evenly and in less time. Place the breasts in a baking dish and bake them for 20 minutes, or until an instant-read thermometer inserted into the thickest part just reads 160°F. Be sure not to overcook the chicken breasts, as they are very lean. Remove from the oven, cover lightly with foil, and rest for five minutes before slicing and serving.