Rinse the leeks well and slice into 1/4-inch thick half moons.

Preheat the oven to 375°F.

Season the chicken thighs with salt, pepper, and paprika.

Heat a large oven-safe skillet over high heat. Sear the chicken thighs until browned on all sides, about 5 minutes per batch. Set aside.

Reduce heat to medium-low. Add butter to the skillet and cook the leeks until soft, about 6-8 minutes. Add mushrooms, salt, and cook covered for 5 minutes.

Sprinkle flour over vegetables, stir, then add chicken broth and sherry. Simmer for 2-3 minutes.

Return chicken to the skillet, spoon sauce over, and transfer to the oven. Bake covered for 40-50 minutes until cooked through and tender.