3 tablespoons unsalted butter
3 tablespoons unbleached flour
3 cups milk, warmed
Sea salt  and freshly cracked pepper
In a saucepan, melt the butter over medium-high heat. Add the flour and mix with a whisk until it forms a blond roux (the fancy French term for “flour and butter”—blond refers to its color, which means it cooks a minute or two, turning slightly golden). Add the heated milk one cup at a time, whisking to incorporate. Bring to a soft boil, always whisking, and then add the salt, pepper, and grated nutmeg. Reduce the heat to medium and whisk it periodically until the sauce thickens to a milkshake consistency, about 10 minutes.