4tablespoons(60grams)butteror dairy-free butter, or 3 tbsp olive oil
2cups(500grams)milkor unsweetened soy milk
½teaspoon(2pinches)salt
1pinchnutmeg and black pepper(optional)
Melt butter (or warm the oil) in a saucepan with a heavy bottom on medium heat.
Add the flour and whisk fast and continuously for 1 to 2 minutes until the flour-fat mixture (called a roux) starts to bubble and turn golden brown.
Add milk to the pot all at once, then on low heat, whisk the sauce until it thickens. Season with salt, nutmeg, and black pepper.Tip: to speed up this step, you can warm the milk (up to 180°F or 80°C and never boiling) in a separate pot, then add the hot milk to the saucepan with the roux. This way, you'll need to whisk a lot less time.
Taste and adjust for salt and keep in mind that the white sauce will keep thickening as it cools down.If you don't use it immediately, remember to stir it from timeto time as it cools down to avoid lumps.