Step 1: Season the chicken breasts with salt and pepper on both sides, then dredge them in flour, shaking off any excess.
Step 2: Heat olive oil and 1 tablespoon of butter in a large skillet over medium-high heat. Sear the chicken for 5-6 minutes per side until golden brown and cooked through (165°F internal temperature). Remove and set aside.
Step 3: In the same skillet, add the remaining 2 tablespoons of butter. Once melted, add the minced garlic and sauté for 30-60 seconds until fragrant.
Step 4: Pour in the chicken broth to deglaze the pan, scraping up any browned bits from the bottom. Let it simmer for 2 minutes to reduce slightly.
Step 5: Reduce heat to medium-low and stir in the heavy cream and Parmesan cheese. Simmer for 3-5 minutes until the sauce begins to thicken.
Step 6: Add the fresh baby spinach to the skillet and stir constantly until the leaves are wilted and incorporated into the sauce.
Step 7: Return the chicken to the skillet, spooning the sauce over the meat. Let it warm through for 1-2 minutes and finish with a squeeze of lemon juice if desired before serving.