Before you start cooking, mince your garlic and chop the parsley so everything's ready when you need it. Pat the chicken thighs completely dry using paper towels to remove excess moisture so the chicken will brown properly. In a small bowl, combine onion powder, paprika, salt, and pepper. Rub the chicken thighs generously with the seasoning mixture and set aside.

Arrange the green beans in a microwave-safe dish with 1/2 cup water and cook in the microwave for 8-10 minutes until almost done but still crisp. The beans should be bright green and easy to pierce with a fork. Drain well and set aside.

Heat a large cast iron skillet over medium-low heat and melt 2 tablespoons of butter until it starts to foam gently. If the butter smokes, your pan is too hot. Place the seasoned chicken thighs in the hot skillet without crowding and cook until crispy, about 5-6 minutes. Flip and cook another 5-6 minutes until cooked through and a cooking thermometer displays 165°F (75°C). The juices should run clear. If the chicken browns too quickly, lower the heat. Transfer chicken to a plate and cover loosely with foil.

In the same skillet, reduce heat to low and melt the remaining tablespoon of butter. Add chopped parsley, minced garlic, hot sauce, and red crushed chili pepper flakes. Stir constantly for about 30 seconds until fragrant but not browned. Add the pre-cooked green beans and cook for 4 to 5 minutes, stirring regularly, until cooked to your liking.

Add lemon juice and chicken stock to the skillet, scraping up any browned bits from the bottom of the pan. Reduce the sauce for 2-3 minutes until slightly thickened and it coats the back of a spoon. Push green beans to the side, place the chicken back in the pan with the sauce, and reheat quickly for 1-2 minutes. Adjust the seasoning with pepper.

Serve the lemon garlic butter chicken thighs warm, garnished with more crushed chili pepper, fresh parsley, and a slice of lemon if you like.