Pat the chicken thighs completely dry with paper towels, pressing firmly to remove all moisture. In a small bowl, combine garlic powder, onion powder, paprika, salt, and pepper. Rub the seasoning evenly over both the skin side and underside of each chicken thigh.
Heat the olive oil in a 12-inch cast iron skillet over medium heat. Place the chicken thighs skin-side down, ensuring they are not crowded, and cook undisturbed for 7-8 minutes until they are deep golden brown and the skin releases easily from the pan. Flip the thighs and cook for an additional 10-12 minutes until the internal temperature reaches 165°F when checked with an instant-read thermometer. Transfer the chicken to a plate and tent with foil.
In the same skillet, melt the butter over medium heat. Add the minced shallot and garlic, sautéing for about 1 minute until fragrant but not browned.
Pour in the chicken broth and lemon juice. Add the thyme sprigs and crushed red pepper flakes. Use a wooden spoon to scrape up any browned bits from the bottom of the pan. Reduce the heat to low and stir in the heavy cream.
Simmer the sauce for 5-6 minutes, stirring occasionally, until it thickens enough to coat the back of a spoon. If the sauce seems thin, simmer for another 1-2 minutes. Return the chicken to the skillet with any accumulated juices. Spoon the sauce over the chicken, garnish with parsley, and serve hot.
