1. Season the chicken breasts with salt and pepper on both sides.
2. In a large skillet, heat the olive oil over medium-high heat. Add the chicken breasts and cook for 6-7 minutes on each side until golden brown and cooked through. Remove from the skillet and set aside.
3. In the same skillet, add the minced garlic and sauté for about 30 seconds until fragrant.
4. Pour in the chicken broth, scraping up any bits from the bottom of the skillet. Stir in the heavy cream and Dijon mustard, bringing the mixture to a simmer.
5. Add the Parmesan cheese and stir until melted and the sauce thickens, about 3-4 minutes.
6. Stir in the fresh spinach until just wilted, then add the lemon juice for a touch of brightness.
7. Return the chicken breasts to the skillet, spooning the sauce generously over them. Let everything simmer for an additional 2-3 minutes to meld the flavors.
8. Optional: Sprinkle with red pepper flakes for a hint of spice before serving.

Cooking with my abuela taught me to trust my senses, so feel free to adjust the seasoning and sauce consistency as you go. The key is to enjoy the process as much as the result.