Begin by heating 1 tablespoon of olive oil in a large skillet over medium heat. Add the diced onion and sprinkle with ½ teaspoon of kosher salt. Sauté for about 3-4 minutes until the onion becomes translucent. Then stir in the minced garlic and dried thyme, cooking for an additional minute until fragrant.
Next, add 2 tablespoons of unsalted butter to the skillet. Once melted, sprinkle in 2 tablespoons of all-purpose flour, stirring constantly to form a roux. Cook for about 1-2 minutes until it turns a light golden color.
Gradually whisk in 1 cup of whole milk, ensuring there are no lumps. Continue to stir until the mixture thickens, which should take about 3-5 minutes. Season with ½ teaspoon of ground nutmeg and adjust salt to taste.
Once your sauce is ready, add the 16 ounces of dried gnocchi directly into the skillet. Stir gently to coat the gnocchi in the creamy sauce. Allow it to cook for about 5-7 minutes, or until the gnocchi float to the surface, indicating they are cooked.
Fold in 4 ounces of fresh spinach and 1 cup of grated Parmesan cheese. Stir until the spinach wilts and the cheese melts into the sauce, creating a creamy consistency.
Finally, squeeze the juice of 1 lemon over the gnocchi, stirring to combine. This brightens the dish and enhances the flavors beautifully.