16ozfrozen chopped spinachthawed and squeezed very dry
2tbspunsalted butter
3clovesgarlicminced
1/4cupyellow onionfinely diced
2tbspall-purpose flour
1cupheavy cream
1/4cupwhole milkor more cream
1/4tspfreshly grated nutmegor 1/8 tsp pre-ground
1/4tspkosher saltplus more to taste
1/4tspblack pepper
1/4cupParmesan cheesefreshly grated
Instructions
Prep the Spinach
Thaw the frozen spinach completely. Transfer it to a clean kitchen towel or several layers of paper towels and squeeze out as much water as possible — squeeze hard and repeatedly until no more liquid comes out. Set aside.
Finely dice the onion and mince the garlic. Have all your remaining ingredients measured and ready before you start cooking, as the sauce comes together quickly.
Build the Cream Sauce
Melt the butter in a large skillet over medium heat. Add the diced onion and cook, stirring occasionally, for 3–4 minutes until softened and translucent. Add the minced garlic and cook for another 30 seconds until fragrant.
Sprinkle the flour over the onion and garlic mixture and stir constantly for 1 minute to cook off the raw flour taste. The mixture will look a bit pasty — that's exactly right.
Slowly pour in the heavy cream and milk, whisking constantly to prevent lumps. Continue to cook over medium heat, whisking, for 2–3 minutes until the sauce thickens enough to coat the back of a spoon.
Stir in the nutmeg, salt, and black pepper. Taste the sauce and adjust seasoning as needed.
Finish and Serve
Add the squeezed-dry spinach to the skillet and stir well to combine with the cream sauce. Cook over medium-low heat for 2–3 minutes, stirring frequently, until the spinach is heated through and fully coated in the sauce.
Remove from heat and stir in the freshly grated Parmesan cheese until melted and smooth. Taste once more for seasoning, adding more salt, pepper, or nutmeg as desired.
Transfer to a serving dish and serve immediately. Garnish with an extra pinch of nutmeg or a little more Parmesan if desired.
Notes
Make Ahead: Prepare up to 4 days in advance and store in an airtight container in the fridge. Reheat gently in a skillet with a splash of cream or milk. Freezer Friendly: Freeze for up to 2 months; thaw overnight before reheating. Richer Version: Add 2 oz softened cream cheese along with the heavy cream for an extra-thick, velvety texture. Fresh Spinach: Use 20 oz fresh baby spinach — wilt in batches in the skillet, drain well, then proceed with the recipe.