Chicken with Ginger-Peanut Sauce on Warm Spinach

Preparation and cooking time:   25 minutes
    The chicken is served on barely warmed spinach with a light peanut vinaigrette  I cut the breasts in half, the short way.  They cook a bit faster and it makes a nicer presentation.

2 chicken breasts, boneless, skinless
6 - 8oz fresh spinach, for salad
1/2 onion
2 cloves garlic
4 slices fresh ginger
2 tsp oil
2 tsp sesame oil
3 tbs peanut butter
1 tbs soy sauce
1/2 cup chicken stock
1 tbs sherry vinegar

Roughly chop onion.  Mince ginger and garlic.  Heat oil in a large, nonstick skillet.  Add garlic, onion, ginger and sauté briefly.  Add chicken and brown on both sides.  Add stock and peanut butter, stirring well to combine.  Cover, reduce heat and simmer until chicken is cooked through, about 10 minutes. 
Prepare spinach, wash if needed, and spin dry. When chicken is done, remove to a plate.  Spoon 3/4 of the sauce on top and cover to keep warm.  Add the vinegar to the remaining sauce in the skillet and stir well.  Remove skillet from heat.  Add spinach and toss gently to combine with the vinaigrette until just barely wilted.  Divide the spinach between two plates, top with chicken and sauce. Serve.