4 tablespoons unsalted butter
¼ cup all purpose flour
4 garlic cloves, minced
1 large shallot, minced (¼ cup)
¾ cup heavy cream, room temperature
¾ cup whole milk, room temperature
Pinch freshly grated nutmeg
fresh finely ground black pepper
1 pound fresh baby spinach, washed, dried very well
1 cup freshly shredded good quality Gruyere cheese (about 3 ounces)
Melt butter in a 6-quart pot over medium heat. Slowly whisk in flour until smooth. Stir in garlic and shallots and sauté until tender, about 1 minute. Slowly whisk in heavy cream and milk until smooth. Season with nutmeg, 1½ teaspoons salt and 4 turns on the pepper mill.
Bring to a boil over medium-high heat. Reduce to simmer and cook until raw flour flavor cooks out, about 3 minutes. Stir periodically.
Add spinach. Cover and increase the heat to medium, to steam and slightly wilt the spinach, about 1 minute. Remove lid and stir (using a rubber spatula) the hot cream sauce from the bottom over the top of the spinach, further wilting the spinach. Continue stirring until all the spinach has wilted, about 2 minutes. Remove from the heat.
Stir in the Gruyere until melted. Remove to a small casserole dish. Serve family style.