Step 1: Grab a medium-sized blow and whisk in your chicken stock, mustard, lemon juice, chilli flakes and rosemary. Season with salt.
Step 2: Grab a skillet and place this over medium heat until hot, 1-2 minutes. Season your chicken with kosher salt and pepper. Place your chicken skin side down and place a smaller skillet or someone heavy on top of the chicken to weigh it down so as to flatten them a little. Cook until your skins are a nice golden brown and are crispy about 7-9 minutes.
Step 3: Now that they're nice and crispy, flip your chicken over and reduce the heat to medium-low. Add in your minced garlic and cook until your chicken is cooked right through, 2-3 minutes. Place your chicken pieces onto a platter. Grab the chicken stock you prepared earlier and add this mixture to your skillet. Cook and scrape any brown bits or until you see it slightly thickened about 1-2 minutes. Grab a spoon and pour this over your chicken pieces.