Melt 2 tbsp of the butter in a large skillet over med-heat. Once melted, add the seasoned chicken breasts and cook for 4-5 minutes – or until cooked through. They should be golden brown on both sides. Remove from the skillet and let them rest on a plate while you make the sauce.
Add the remaining butter to the pan with the garlic, cooking until fragrant. Reduce the heat to low and add the heavy cream and sun-dried tomatoes. Bring to a simmer. Stir in the spinach and parmesan, simmering until the cheese has melted.