Prep the Chicken: Pat chicken dry with paper towels. Season both sides with salt, pepper, garlic powder, and smoked paprika.
Pound thicker pieces to about 3/4 inch so they cook evenly.
Sear the Chicken: Heat olive oil and butter in a large skillet over medium-high heat. Add chicken and cook 4–6 minutes per side, until golden and cooked through (internal temp 165°F). Transfer to a plate and tent with foil.
Sauté the Garlic: Reduce heat to medium.
In the same skillet, add minced garlic. Stir for 30–60 seconds until fragrant. Do not let it brown.
Deglaze: Pour in chicken broth, scraping up browned bits.
Simmer 1–2 minutes to reduce slightly.
Build the Sauce: Add milk and bring to a gentle simmer. Stir in the cornstarch slurry and simmer 1–2 minutes until slightly thickened.
Add Parmesan: Reduce heat to low. Stir in Parmesan until melted and smooth.
If the sauce gets too thick, add a splash of broth or milk.
Finish with Yogurt and Lemon: Remove the pan from heat and whisk in Greek yogurt, lemon zest, and lemon juice. This keeps the yogurt from curdling and gives the sauce a fresh lift.
Add Spinach: Put the skillet back over low heat, add spinach, and stir until just wilted, 30–60 seconds. Season to taste with salt, pepper, and red pepper flakes.
Return the Chicken: Nestle the chicken back into the sauce and spoon sauce over the top.
Warm for 1–2 minutes.
Serve: Garnish with fresh parsley or basil and extra Parmesan. Serve over zucchini noodles, steamed veggies, roasted potatoes, or whole-grain pasta.