How do I make a white sauce without dairy?

The mechanics of a dairy-free béchamel are identical to a dairy one — fat, flour, liquid. Two things change. Some plant milks curdle or thin when they are heated with flour and acid, so the choice of milk matters more than it does with cow's milk. And a plant milk contributes almost nothing in flavour, so a sauce that would have tasted of milk and butter tastes of nothing unless you build the savour back in deliberately.

What you'll need

• Oat or unsweetened soya milk
• Olive oil or a block dairy-free spread
• Plain flour
• Nutritional yeast (optional)
• Dijon mustard (optional)
• Nutmeg (optional)

Step by step

1. Choose the milk on how it behaves, not on taste alone.Oat milk is the best all-rounder — creamy, stable and neutral, and barista versions are stabilised further. Unsweetened soya is the most protein-rich and gives the closest body to dairy, but curdles with acid. Avoid sweetened or vanilla varieties entirely, and avoid rice milk, which is thin and sweet.
2. Check the carton says unsweetened.This is the most common mistake and it ruins the dish rather than merely weakening it. A sweetened oat milk makes a lasagne taste like pudding, and there is no correcting it afterwards.
3. Make the roux with olive oil or a firm dairy-free block.Same weight as you would use of butter — 25g of fat to 25g of flour per 500ml. Olive oil works and brings its own flavour, which suits a lasagne. A block-style spread behaves most like butter. Avoid soft tub spreads with a high water content; they spit and the roux does not come together.
4. Cook the roux for two to three minutes, then add the milk gradually.Exactly as for a dairy version — a splash at a time, whisked completely smooth before the next. Plant milks are thinner than dairy so the sauce may look loose for longer before it takes.
5. Simmer for five minutes and then build the flavour back.Two tablespoons of nutritional yeast for a cheesy savour, a teaspoon of Dijon, a good grating of nutmeg, salt, and white pepper. Taste and keep going — it needs more seasoning than a dairy sauce, not less.
6. Add a fat at the end for richness if it tastes thin.A tablespoon of olive oil or a spoonful of a plant cream whisked in off the heat gives the coating quality that dairy fat was providing. Fat is usually what a dairy-free sauce is short of, not thickness.

Tips

• Soya milk curdles readily with acid. Do not add lemon, wine or tomato to a soya béchamel, and add it to an acidic dish last and off the heat.
• Nutritional yeast is the single most useful ingredient here. It supplies the glutamate that dairy would have brought, which is what makes a sauce taste savoury rather than merely creamy.
• A dairy-free cheese sauce works better with nutritional yeast plus mustard plus a little miso than with dairy-free cheese, which often melts into an oily layer rather than dispersing.
• Plant milks catch and scorch more readily than dairy milk. Use a heavy pan and keep the heat lower than you would otherwise.
• Warm the plant milk before adding it. Cold plant milk into a hot roux is more prone to seizing into clumps than cold dairy milk is.

Alternatives

• Cashew cream base: Cashews soaked in hot water for half an hour and blended with water to the consistency of single cream. Rich, genuinely creamy, and needs no roux at all — it thickens by itself when heated. The best dairy-free option for a stroganoff or a pasta sauce, and it freezes acceptably.
• Cauliflower or potato purée: Cooked cauliflower or floury potato blended with stock and a little oil gives a thick, mild sauce with no flour and no plant milk. It is not a béchamel but it does the same job in a bake and it is far cheaper than nut creams.
• Coconut milk: Works where the dish can carry the flavour, which is fewer places than people hope. Excellent in a curry or a spiced bake, wrong in a lasagne or a fish pie.
• Bought dairy-free white sauce: Sold in jars and cartons, usually oat or soya based with added starch. Convenient and consistent, and worth the money if you are cooking one dish, but noticeably sweeter than a homemade version.

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