Preheat the oven to 375 degrees.
Heat your cast iron or oven safe skillet on medium heat until it is thoroughly hot.
While heating, pat dry your chicken thighs and sprinkle the skin with salt.
Lay the chicken thighs skin side down in the hot pan, making sure to not overcrowd the pan or move them once the skin hits the pan.
Sprinkle the tops of the chicken with salt.
Sear the chicken skin until it releases and is golden brown. This will take several minutes.
Once they are seared, carefully flip the chicken over.
Place the oven-safe skillet in the oven and cook the chicken at 375 degrees for 15-20 minutes or until the thickest part of the chicken is at least 165 degrees.
While the chicken cooks, prep your sauce components.
Remove the skillet from the oven. Remove the chicken from the skillet, setting aside on a plate, and return the skillet to the stovetop burner over medium heat.
In the chicken fat, saute the shallot or onion until translucent, or about 5 minutes.
Add the minced garlic and saute for 1 minutes, making sure not to let the garlic burn.
Sprinkle the mixture in the skillet with 1 tablespoon of AP flour. Toast the flour for 1-2 minutes, stirring continuously.
Add mustard, herbed salt, wine, and the stock. If you are subbing stock for wine, add all of the stock at this point. Stir to completely combine the sauce and cook for 2 minutes. Season as desired with black pepper.
Plate your chicken and sauce as desired. To keep the crispy skin, put the sauce on the plate first, then nestle your chicken on top.