Remove chicken thighs from the refrigerator 15 minutes before cooking. Pat each thigh completely dry with a paper towel to remove surface moisture -- this is essential for a proper golden sear.

In a small bowl, combine paprika, onion powder, salt, and black pepper. Rub the seasoning mixture generously over both sides of the chicken thighs right before cooking.

Place trimmed green beans in a microwave-safe dish with 1/2 cup of water. Microwave on high for 8 to 10 minutes until nearly tender but still slightly firm. Drain and set aside.

Heat a large cast iron skillet over medium-low heat and melt 2 tablespoons of butter. Wait until the butter is fully melted and just beginning to foam.

Add the seasoned chicken thighs to the skillet in a single layer. Cook for 5 to 6 minutes without moving them until the underside is deep golden. Flip and cook another 5 to 6 minutes until an instant-read thermometer reads 165 degrees Fahrenheit (75 degrees Celsius). Lower the heat if browning too quickly. Transfer to a plate.

Lower the heat and melt the remaining 1 tablespoon of butter in the same skillet. Add the minced garlic, chopped parsley, Sriracha, and red pepper flakes. Stir constantly for 1 minute until fragrant.

Add the par-cooked green beans to the skillet. Cook for 4 to 5 minutes, stirring regularly, until they reach your preferred tenderness.

Pour in the lemon juice and chicken stock. Let the sauce reduce for 2 minutes, stirring occasionally, until slightly thickened and glossy.

Push the green beans to the side and return the chicken thighs to the skillet. Reheat for 1 to 2 minutes, spooning the sauce over the chicken. Taste and adjust seasoning with pepper.

Serve immediately, garnished with fresh parsley, extra red pepper flakes, and lemon slices.