Mix together all the seasonings and set aside.
Pat the chicken thighs dry on all sides and then coat well in the seasoning mix.
Preheat oven to 325F.
In a large oven-safe skillet (with a lid) over medium heat, add olive oil to the skillet and then place each chicken thigh skin side down. Cook about 3-4 minutes per side, making sure to get the skin nice and crispy.
Add the dijon mustard, garlic, and leeks to the pan and stir a little. Sauté a few minutes.
Pour bone broth all over and then top with fresh herbs.
Cover and place in oven for 40-45 minutes.
Serve over grains, rice, mashed potatoes.