In a small bowl, whisk together milk, broth, and cornstarch until smooth.
¾ cup milk, ¼ cup chicken broth, 1½ tsp cornstarch
Season chicken with black pepper and Italian seasoning.
1 lb chicken breasts, ½ tsp Italian seasoning, ½ tsp black pepper
Heat olive oil in a skillet over medium heat. Cook chicken 4–5 minutes per side until golden and cooked through. Remove and set aside.
1 tsp olive oil
In the same skillet, sauté onion and mushrooms for 5–6 minutes until softened. Add garlic and cook 30 seconds.
½ small onion, 1 cup mushrooms, 2 cloves garlic
Stir in sun-dried tomatoes and spinach. Cook until spinach wilts.
¼ cup sun-dried tomatoes, 2 cups spinach
Pour in milk mixture and simmer gently for 2–4 minutes until slightly thickened.
Return chicken to the skillet and spoon sauce overtop.