Wash and roughly chop the Spinach. Pat or squeeze out excess moisture so the leaves aren't too wet when cooking.
Heat a tablespoon of Extra-Virgin Olive Oil in a large skillet over medium heat, add minced Garlic and cook until fragrant but not browned, about 30 seconds.
Add the Spinach in batches, turning until wilted and tender; transfer the wilted greens to a bowl and squeeze out any remaining liquid, then roughly chop if needed.
Return the pan to medium-low heat and add another tablespoon of Extra-Virgin Olive Oil. Sprinkle in the All-Purpose Flour and stir continuously for 1–2 minutes to cook the raw taste out of the flour and form a light roux.
Slowly whisk in the Milk a little at a time, scraping up any browned bits and smoothing out lumps, then simmer until the sauce thickens to a creamy consistency.
Stir the wilted Spinach back into the sauce and cook for a minute to meld flavors. Add a splash of White Wine Vinegar to brighten the dish, then season with Salt, freshly ground Black Pepper, and a pinch of grated Nutmeg.
Taste and adjust seasoning or consistency (add a splash more Milk if you prefer it looser). Serve the esparregado warm as a rich, flavorful side.
