Béchamel Sauce for Lasagna

Melt butter in a heavy-bottomed, medium saucepan over medium-low heat.

Add flour, whisking constantly. Cook, whisking occasionally, 2 to 3 minutes; do not let roux brown.

Whisking constantly, add about 2 tablespoons hot milk to saucepan.

Pour half of the remaining hot milk into the saucepan in small increments, whisking the mixture constantly, until a smooth paste forms.

Whisk remaining milk into pan; add nutmeg and salt.

Cook, stirring with a wooden spoon, making sure to scrape bottom and sides, until sauce is thick and creamy, about 15 minutes; if any lumps form, stir sauce rapidly with a whisk.

Season with pepper; remove from heat. Let sauce stand until lukewarm, about 30 minutes, before assembling lasagna.