Pat the chicken thighs dry thoroughly with paper towels. In a shallow dish or plate, combine salt, black pepper, garlic powder, and dried thyme. Dredge each chicken thigh in the seasoning mix, ensuring it's evenly coated on all sides.

Heat the olive oil in a large cast-iron skillet (10-12 inch) over medium-high heat until shimmering.

Carefully place the seasoned chicken thighs in the hot skillet. Sear for 5-7 minutes per side, or until deeply golden brown and cooked through (internal temperature reaches 165°F/74°C). Remove chicken from the skillet and set aside on a plate, tented loosely with foil, to rest.

Reduce the heat to medium. Add butter to the same skillet, scraping up any browned bits from the bottom with a wooden spoon or spatula. Once melted, sprinkle in the flour and whisk continuously for 1-2 minutes, creating a light roux.

Add the minced garlic and cook for another 30 seconds until fragrant.

Gradually pour in the chicken broth, whisking constantly to prevent lumps. Bring the mixture to a simmer, then cook, stirring occasionally, for 3-5 minutes, or until the gravy thickens to your desired consistency.

Stir in the heavy cream, if using, and cook for an additional minute. Taste and adjust seasoning with salt and pepper if needed.

Return the rested chicken thighs to the skillet, spooning the gravy generously over them. Garnish with fresh chopped parsley. Serve immediately with mashed potatoes, rice, or egg noodles for a complete meal.