Preheat your oven to 375°F (190°C). If you’re using a skillet that goes from stove to oven, you’re in luck—no extra dish needed.
Season the chicken thighs with salt and pepper. In a skillet, heat the olive oil over medium-high heat and brown the chicken on both sides, about 3–4 minutes per side. You don’t need to cook it through; just get a nice color.
Remove the chicken and set aside. In the same skillet, add the minced garlic and sauté for about 30 seconds until fragrant.
Pour in the chicken broth, scraping up any browned bits from the bottom. Stir in the heavy cream, lemon juice, Dijon mustard, oregano, and red pepper flakes. Let the sauce simmer gently for 2–3 minutes.
Stir in the sun-dried tomatoes and spinach. Return the chicken to the pan, spooning some sauce over the top. Sprinkle Parmesan over everything.
Transfer the skillet to the oven (or move to a casserole dish if your pan isn’t oven-safe) and bake for 15–20 minutes, until the chicken is cooked through and the sauce has thickened.
Let it rest for a few minutes, then serve with crusty bread, pasta, or a simple side of vegetables. If you like extra brightness, a quick squeeze of fresh lemon over the top works beautifully.