Step 1
Preheat oven to 350°. Pat 1½ lb. skin-on, bone-in hen thighs (about 4 small) dry and season generously throughout with kosher salt. Sprinkle evenly on either side with 2 tsp. all-purpose flour.
Step 2
Warmth 1 Tbsp. extra-virgin olive oil in a big cast-iron or high-sided skillet over medium. Cook dinner hen thighs, pores and skin facet down, undisturbed, till thighs launch simply from pan, 7–9 minutes. Flip hen over and cook dinner on different facet till golden brown beneath, about 5 minutes. Switch hen to a plate and prepare pores and skin facet up (they gained’t be absolutely cooked by at this level).
Step 3
Cook dinner 1 medium crimson onion, sliced into 2″-thick wedges, in identical pan, stirring sometimes, till barely softened and beginning to flip golden brown, about 5 minutes. Add 6 garlic cloves, coarsely chopped, and 4 thyme sprigs and cook dinner, stirring, till garlic is aromatic, 1–2 minutes.
Step 4
Pour in ⅓ cup apple cider vinegar, scraping up any browned bits. Add 2 Tbsp. Dijon mustard, 2 Tbsp. honey, 1 Tbsp. Worcestershire sauce, 1 tsp. freshly floor pepper, and ¼ cup water and stir to mix. Take away pan from warmth and blend one 1-lb. bag frozen sliced peaches into onion combination. Return hen to skillet, arranging pores and skin facet up.
Step 5
Switch pan to oven and bake simply till peaches and hen thighs are cooked by (an instant-read thermometer inserted into the thickest a part of a thigh with out touching the bone ought to register 165°), 17–20 minutes.
Step 6
Take away pan from oven and scatter a number of extra thyme sprigs over hen to serve.
