Preheat your oven to 425 degrees Fahrenheit. This high heat is essential for achieving a crispy skin on the chicken, which adds a wonderful texture to the dish.
In a large bowl, whisk together balsamic vinegar, honey, whole grain mustard, minced garlic, and a generous sprinkle of salt and freshly ground black pepper. Taste the mixture; it should be a delightful balance of sweet and tangy.
Add the chicken thighs to the bowl and toss them to coat thoroughly in the marinade. It’s best to let them marinate at room temperature for about 20 minutes, or you can refrigerate them for up to one hour for deeper flavor.
Once marinated, remove the chicken from the marinade, reserving the marinade for later. Pat the chicken dry with paper towels; this is crucial for achieving that coveted crispy skin.
In a 12-inch oven-safe skillet, heat olive oil over medium-high heat until shimmering. Adding the chicken skin-side down, it should sizzle as it hits the pan, which is a good sign!
Cook the chicken for about 2 to 3 minutes, or until the skin is nicely browned. This step locks in the flavor and creates a beautiful golden crust.
Carefully flip the chicken over, and add in the grape tomatoes. Cook for an additional 5 minutes until the tomatoes start to burst and release their juices.
Pour the reserved marinade over the chicken and toss in the rosemary sprigs. This will bring incredible flavor as the chicken cooks.
Bring the mixture to a boil, then transfer the skillet uncovered to the preheated oven. Bake until the chicken reaches an internal temperature of 165 degrees on an instant-read thermometer, which should take about 20 minutes.
Once done, remove from the oven and discard the rosemary stems. Allow the chicken to rest for a few minutes before serving, ensuring it stays juicy and tender.
