Place plastic wrap over each chicken breast and pound to about ½-inch thickness for even cooking. Pat dry.
Combine all chicken dredge ingredients in a shallow bowl. Coat chicken evenly and shake off excess.
Heat olive oil and butter in a large skillet over medium-high heat.
Add chicken and cook 4–5 minutes per side until golden and cooked through. Work in batches if needed. Remove and set aside.
Turn heat off and add chicken broth. Set heat to medium and scrape the bottom of the pan to release flavorful bits. Simmer until reduced by half, about 6–7 minutes. Add garlic during the last minute.
Warm the half and half slightly (about 40 seconds in microwave). Gradually stir into the skillet. Bring to a gentle simmer, then reduce heat to low.
Stir in softened cream cheese until smooth and creamy.
Add fresh spinach and cook until wilted. Stir in lemon juice if desired.
Return chicken and any juices to the skillet. Cover and heat through. Garnish with fresh parsley and serve your creamy Chicken Florentine warm.