Pat chicken thighs completely dry with paper towels. This is crucial for crispy skin. Season both sides with 3/4 tsp salt, pepper, and smoked paprika. Let sit at room temperature for 15 minutes while you prep the vegetables.

Heat oil in a large oven-safe skillet over medium-high heat until shimmering. Add chicken skin-side down and cook without moving for 6-7 minutes until the skin is deeply golden and releases easily from the pan. Flip and cook 3 minutes more. Transfer to a plate; the chicken will not be fully cooked yet.

Pour off all but 2 tablespoons of fat from the pan. Add onions and remaining 1/4 tsp salt. Cook over medium heat, scraping up the browned bits, until onions are softened and starting to caramelize, about 8 minutes. Add mushrooms and cook until they release their moisture and begin to brown, another 5 minutes.

Stir in garlic and cook 30 seconds until fragrant. Sprinkle flour over the vegetables and stir constantly for 1 minute to cook out the raw taste. Slowly whisk in chicken broth, then cream. Bring to a simmer and cook until thickened enough to coat the back of a spoon, about 3 minutes.

Nestle chicken thighs skin-side up into the gravy, making sure the skin stays above the liquid. Transfer to a 375°F oven and roast for 15-18 minutes until the internal temperature reaches 165°F. Let rest 5 minutes, then sprinkle with fresh thyme before serving.