Pound chicken: Pat the chicken breasts dry with paper towels. Place them between two sheets of plastic wrap and pound them lightly with a meat mallet, especially in the thicker middle part, so they cook evenly. Season them with paprika, salt, and pepper.4 boneless skinless chicken breasts + 1 teaspoon sweet paprika + ½ teaspoon fine sea salt + ¼ teaspoon ground black pepper
Sear chicken: Heat the oil in a Dutch oven or large skillet. Sear the chicken breasts for about 3 minutes per side until lightly golden. Remove them from the pan.2 tablespoons olive oil
Cook mushrooms: Melt the butter in the same pan. Add the mushrooms and cook for about 3 minutes, stirring occasionally. Add the onion and cook for another 2–3 minutes until softened.1 tablespoon butter + 9 oz mushrooms + 1 onion
Add liquids: Pour in the chicken broth and heavy cream. Add the rosemary and a small pinch of salt and pepper. Stir well to combine.1 cup chicken broth + ¾ cup heavy cream + 1 sprig rosemary
Simmer: Return the chicken to the pan and nestle it into the sauce. Reduce the heat to medium-low and simmer for about 10 minutes.
Prepare spinach: In the meantime, wash the spinach in a sieve and let it drain well.5.5 oz baby spinach
Finish dish: Add the spinach to the pan and gently push it into the sauce with a spoon. Cover the pan and cook for another 10 minutes or until the spinach has wilted and the chicken is cooked through. The internal temperature should reach 165°F/74°C.
Thicken (optional): For a thicker sauce, mix 1 teaspoon cornstarch with 1–2 teaspoons cold water and stir it into the sauce during the last few minutes of cooking.
Adjust the taste with salt and pepper and serve.
Notes
Spinach: You can use fresh or frozen spinach. If using frozen spinach, you will need about 3–4 oz (75–100 g). Thaw and squeeze it well to remove excess water before adding it to the sauce. Fresh spinach cooks down a lot, so you need a much larger amount to start with.
Check the meat: If you don’t have a thermometer, cut into the thickest part of the chicken breast. The meat should be completely white, and the juices should run clear with no pink remaining.