Prep the chicken: Pat the chicken cutlets dry.
Season both sides with salt, pepper, and the smoked paprika if using.
Brown the chicken: Heat the olive oil in a large nonstick skillet over medium-high heat. Add the chicken in a single layer and sear 2–3 minutes per side until lightly golden. Transfer to a plate; it will finish cooking in the sauce.
Sauté the aromatics: Reduce heat to medium.
Add the onion and a small pinch of salt. Cook 2–3 minutes until translucent. Stir in the garlic and cook 30 seconds until fragrant.
Cook the mushrooms: Add the mushrooms.
Let them sit for a minute to brown, then stir. Cook 5–6 minutes until they release moisture and turn golden. Sprinkle in the thyme and oregano.
Deglaze and simmer: Pour in the chicken broth, scraping up any browned bits from the pan.
Simmer 2–3 minutes to reduce slightly.
Make the creamy base: In a small bowl, whisk the Greek yogurt with the Dijon. If you prefer a thicker sauce, whisk the cornstarch into the yogurt now. Turn the heat down to low, then whisk the yogurt mixture into the pan.
Keep heat gentle to avoid curdling.
Finish the chicken: Return the chicken and any juices to the skillet. Spoon sauce over the cutlets and simmer on low 3–5 minutes, until the chicken is cooked through and the sauce is silky. Adjust salt and pepper.
Garnish and serve: Sprinkle with fresh parsley and a light squeeze of lemon if you like.
Serve over steamed greens, cauliflower rice, or a small scoop of brown rice or quinoa.