Preheat oven to 400 F.
Heat a large, ovenproof skillet over medium-high heat.
Add oil to pan.
Season chicken with salt and pepper.
Add chicken to pan, and cook 2 minutes on each side, or until browned.
Remove chicken from pan.
Add broth, syrup, half of thyme (1 teaspoon), and garlic to pan; bring to boil, scraping pan to loosen browned bits.
Cook 2 minutes, stirring frequently.
Add vinegar and mustard; cook 1 minutes stirring frequently.
Return chicken to pan along with any accumulated juices, and spoon sauce over the top.
Bake 10 minutes, or until chicken reaches 165F.
Remove chicken from pan.
Heat skillet over medium heat for 2 minutes, or until liquid thickens to syrup. Watch closely as sauce will thicken quickly.
Serve sauce over chicken, and sprinkle with remaining thyme just before serving.