Prep the chicken: Pat chicken breasts dry and slice horizontally to create thinner cutlets, or cube into bite-size pieces. Season both sides with salt, pepper, and half the Italian seasoning.
Sear the chicken: Heat olive oil in a large skillet over medium-high. Add chicken in a single layer and sear 3–4 minutes per side until golden and just cooked through.
Remove to a plate and tent with foil.
Sauté aromatics: Reduce heat to medium. Add the chopped onion with a pinch of salt. Cook 3–4 minutes until softened.
Stir in garlic and cook 30–60 seconds until fragrant.
Build the roux: Sprinkle flour over the onions and garlic. Stir for 30 seconds to coat. This helps thicken the sauce without heavy cream.
Add liquids: Slowly whisk in chicken broth, scraping up any browned bits.
Add milk, Dijon, remaining Italian seasoning, and red pepper flakes. Simmer 2–3 minutes, stirring, until slightly thickened.
Finish the sauce: Remove the skillet from heat. Whisk in Greek yogurt until smooth.
If the pan is too hot, the yogurt can curdle; off-heat is key for a creamy finish.
Combine: Return chicken and any juices to the skillet. Simmer on low for 1–2 minutes to warm through. Squeeze in lemon juice, taste, and adjust salt and pepper.
Add veggies (optional): Stir in a few handfuls of spinach until wilted, or fold in sautéed mushrooms or steamed broccoli for a fuller meal.
Garnish and portion: Sprinkle with parsley.
Portion into 4 meal prep containers with your sides of choice—steamed green beans, roasted carrots, zucchini noodles, or a small serving of brown rice or cauliflower rice.