Melt the butter in a large sauté pan over medium heat, the add in the garlic. Season with a pinch of salt and a few cracks of pepper, then sauté for about a minute or two until it just starts to turn golden brown.
Throw in the spinach and toss around until it starts to wilt - this will happen very quickly. Sprinkle a little more than half of the parmesan over the top and toss some more.
Remove from the heat to prevent overcooking - you want the spinach to be just wilted - and season with more salt and pepper to taste. Transfer the spinach and all of the juices into a serving bowl, then grate the remaining parmesan over the top and serve.
If using farm fresh stalks of spinach, be sure to give them a good wash before cooking, as they tend to be very sandy. In addition, you'll need to trim off the bulkier stems before cooking, but don't throw them away! They're perfect for juicing, making soups or adding to a green smoothie. If using a box of baby spinach, these steps are not necessary.