Creamed Spinach

INGREDIENT
This makes ~10 servings, you may want to halve it.
 * 3 lb baby spinach (I've used three 10 oz packages of frozen chopped spinach, which was about the right amount)
 * 1 1/4 cups whole milk
 * 1 cup heavy cream
 * 1 small onion, finely chopped
 * 2-3 cloves garlic, finely chopped
 * 1/2 stick (1/4 cup) unsalted butter
 * 1/4 cup all-purpose flour
 * 1/8 teaspoon nutmeg

PREPARATION

 * Defrost and drain frozen spinach, or cook fresh spinach in 2 batches in 1 inch of boiling salted water in an 8-quart pot, stirring constantly, until wilted, 1 to 2 minutes. Drain in a colander and rinse under cold running water until cool. Squeeze small handfuls of spinach to remove as much moisture as possible, then coarsely chop.
 * Heat milk and cream in a small saucepan over moderate heat, stirring, until warm. Meanwhile, cook onion in butter in a 3-quart heavy saucepan over moderately low heat, stirring occasionally, until softened, about 4 minutes. Whisk in flour and cook roux, whisking, 3 minutes. Add warm milk mixture in a fast stream, whisking constantly to prevent lumps, and simmer, whisking, until thickened, 3 to 4 minutes. Stir in nutmeg, spinach, and salt and pepper (be careful not to over-salt, you can always ad more later) to taste and cook, stirring, until heated through.