Season the chicken. Pat the thighs dry with paper towels.
Mix salt, pepper, and paprika, then rub it all over the chicken. Dry skin and even seasoning help great browning.
Brown the chicken. Heat olive oil in a large skillet over medium-high. Place thighs skin-side down and cook without moving for 6–8 minutes, until deeply golden.
Flip and cook 3–5 minutes on the other side. Transfer to a plate. Drain off excess fat, leaving about 1 tablespoon in the pan.
Build the garlic butter base. Reduce heat to medium.
Add butter. When melted and foamy, stir in garlic. Cook 30–60 seconds until fragrant, stirring constantly.
Don’t let it brown.
Deglaze. Pour in chicken stock and scrape up the browned bits. Let it simmer 2 minutes to reduce slightly and concentrate the flavor.
Make it creamy. Stir in cream and Dijon. Simmer gently for 2–3 minutes until the sauce begins to thicken.
If using Parmesan, whisk it in until smooth.
Brighten and season. Add lemon zest and juice. Taste and adjust salt and pepper. The sauce should be savory, garlicky, and balanced with a little lift from lemon.
Finish the chicken. Nestle the thighs back into the pan, skin-side up.
Sprinkle thyme over the top. Simmer on low for 6–10 minutes, or until the chicken reaches 165°F in the thickest part. Spoon sauce over the meat as it finishes.
Garnish and serve. Turn off the heat, scatter with parsley, and give the sauce a final stir.
Serve with mashed potatoes, rice, pasta, or crusty bread to catch every drop.