Trim any extra fat from the chicken thighs, but keep some skin on for added flavor. Season them generously with salt and pepper. Press each thigh into the panko breadcrumbs, coating all sides evenly.

In a large skillet, heat the oil over medium-high heat. Place the chicken thighs skin-side down in a single layer. Let them cook until golden brown on both sides, about 3-4 minutes per side.

Layer the browned chicken thighs in a shallow baking dish (like a 13x9 Pyrex dish). Scatter the sliced onions and garlic over the top, covering the chicken. Cover the dish with foil.

Place the dish in a preheated 350°F oven and bake for about 45 minutes. Remove the foil and bake for an additional 5 minutes, or place under the broiler for 1-2 minutes to crisp the skin, if needed.

Remove the chicken from the baking dish and set aside. Scrape the flavorful drippings and all the tasty bits from the baking dish into a pot. Add the flour to the pot, whisking until it forms a paste.

Slowly pour in the chicken broth, whisking as you go to avoid lumps. Heat this mixture over medium heat, stirring until it boils, then simmer for 3-4 minutes to thicken.

Using an immersion blender, blend the gravy for a smoother finish. Stir in the sour cream, then season with salt and pepper to taste.

Pour the gravy over the baked chicken thighs, and serve while hot. Enjoy with mashed potatoes, rice or fresh biscuits to soak up the gravy.