In a large sauté pan, melt 2 tablespoons unsalted butter over medium heat.

Add 1 clove garlic (pressed or minced) and cook, stirring, about 30 seconds until fragrant (do not brown).

Add 1 cup heavy cream and bring it to a boil.

Lower the heat to maintain a gentle simmer and cook the cream, stirring occasionally, until it has thickened and reduced by half, about 25 minutes.

Stir in ¼ teaspoon kosher salt, freshly ground pepper (to taste), and ¼ teaspoon freshly grated nutmeg.

Working in batches, add the 1 pound fresh spinach leaves: add a handful, toss to coat with the cream sauce and let it wilt before adding the next handful. Repeat until all the spinach is incorporated and the last batch is just barely wilted.

Add ½ cup freshly grated Parmesan cheese and toss with the spinach until the cheese is melted and the leaves are evenly coated.

Remove from the heat (the spinach will continue to cook slightly) and serve warm.