In a small bowl, whisk together maple syrup, balsamic vinegar, garlic, and dried thyme.  Reserve 5-6T of the marinade, cover, and place in the refrigerator.    

Slice boneless skinless chicken breasts in half lengthwise, creating 6 pieces of chicken.  Sprinkle chicken with salt and pepper to taste.  

Place chicken breasts in a gallon sized zip lock bag and pour the remainder of the marinade into the bag with the chicken.  Swish the chicken around in the bag until all pieces are evenly coated.  Place the bag on a plate and leave in the refrigerator overnight.  

The next morning give the bag of chicken a good swish to redistribute the marinade.  Repeat one or two more times during the day if time allows. 

Pre-heat oven to 400 degrees. Place a 21x15 empty baking sheet into the oven while it is pre-heating. 

Meanwhile, scrub and dry sweet potatoes.  Chop into small, even chunks.  Place sweet potatoes in a large bowl and toss with olive oil, salt, and pepper.  Add just enough olive oil so pieces are lightly coated, but not dripping with oil.  

Remove the baking sheet from the oven and evenly distribute the sweet potatoes around the perimeter of the pan, leaving space in the middle for the chicken.  Remove chicken from the refrigerator and place pieces in the center of the baking sheet.  Discard used marinade. 

Spoon or brush half of the 5-6T of reserved marinade over the chicken.  Place baking sheet in the oven and bake for 20-25 minutes, depending on your oven. 

Halfway through baking, remove the pan and give the sweet potatoes a gentle toss to ensure even roasting.  Add the remainder of the reserved marinade to the chicken and finish baking until chicken is cooked completely through.