Step 1: Season the chicken breasts generously on both sides with salt, black pepper, and garlic powder.
Step 2: Heat 1 tablespoon of olive oil in a large skillet or Dutch oven over medium-high heat. Add two chicken breasts and sear for 4-5 minutes per side, until golden brown and cooked through (internal temperature reaches 165°F/74°C). Remove to a plate and cover loosely with foil. Repeat with the remaining chicken breasts, adding the second tablespoon of olive oil if needed.
Step 3: Reduce the heat to medium. Add butter to the same skillet. Once melted, add the minced garlic (and red pepper flakes, if using) and sauté for 1 minute until fragrant, being careful not to burn it.
Step 4: Pour in the chicken broth, scraping up any browned bits from the bottom of the pan with a wooden spoon. Bring to a simmer and cook for 2 minutes to reduce slightly.
Step 5: Stir in the heavy cream and bring to a gentle simmer. Cook for 3-5 minutes, stirring occasionally, until the sauce begins to thicken.
Step 6: Add the fresh spinach to the skillet, a handful at a time, allowing it to wilt before adding more. Continue cooking and stirring until all the spinach is wilted into the sauce.
Step 7: Remove the skillet from the heat and stir in the grated Parmesan cheese until melted and smooth. Taste and adjust seasoning with salt and pepper if necessary.
Step 8: Return the cooked chicken breasts to the skillet, spooning the creamy spinach sauce over them. Garnish with fresh chopped parsley and an extra sprinkle of Parmesan cheese before serving. This truly makes a delightful chicken florentine style meal.