Heat 2 tbs olive oil in a large skillet over medium-high heat until shimmering. Add the chicken thighs in a single layer (work in batches if needed). Sear 4-5 minutes per side until golden-brown and cooked through (internal temperature 165°F / 74°C). Remove chicken to a plate and tent loosely with foil.

Sauce & aromatics

Sauté onion and garlic

Reduce heat to medium. Add the sliced onion to the same skillet; if pan is dry add a scant 1 tbs olive oil. Cook, stirring occasionally, 6-8 minutes until softened and lightly caramelized. Add the minced garlic and cook 30-45 seconds until fragrant.

Deglaze and simmer

Pour in 1 cup chicken broth to deglaze the pan, scraping up browned bits from the bottom with a wooden spoon. Bring to a low simmer and let the broth reduce by about one-third, 3-4 minutes.

Finish the sauce

Stir in 1 cup heavy cream, 1 tbs Dijon mustard, and 1 tbs fresh lemon juice. Simmer gently over medium-low heat 4-6 minutes until the sauce thickens slightly. Taste and adjust seasoning with additional salt and pepper if needed.

Return chicken to sauce

Return the seared chicken thighs and any accumulated juices to the skillet, nestling them into the sauce. Spoon sauce over the chicken and simmer uncovered 3-4 minutes so flavors meld and chicken is reheated through.

Herbs and finishing

Off the heat, stir 1 tbs butter and 1 tsp fresh thyme leaves into the sauce until butter melts and the sauce becomes glossy. Sprinkle 2 tbs chopped fresh parsley over the chicken.

Let rest 2 minutes, then serve the chicken with spoonfuls of the creamy sauce over cooked rice or mashed potatoes and steamed greens if using.