Begin by preheating the oven to 350°F. Chop the vegetables and slice the shallot. Butterfly the chicken breasts by slicing horizontally and leaving only 1/2 inch still connected near the thickest part of the breast.
In separate bowl, whisk together the olive oil, mustard, syrup, salt, pepper and thyme until emulsified.
On a large baking sheet, make it large so that everything has room to spread out and allow the heat from the oven to circulate, toss the chicken, apples, vegetables and shallot with the dressing. Reserve 1-2 tbsp of dressing for after cooking. Bake for 25 minutes or until chicken is cooked all the way through and vegetables and apples are tender.
Drizzle with remaining sauce. Enjoy on its own or over a bed of greens, quinoa or rice.