This classic white onion sauce is creamy, smooth, and full of delicate onion flavor. It’s the perfect winter sauce for serving with lamb, mutton, or even leeks when fresh mint isn’t in season. Simple yet rich, it adds a comforting touch to any meal.
Ingredients Needed:
- 25g (1 oz) butter
- 1 medium onion, finely chopped
- 25g (1 oz) flour
- 300ml (½ pint) hot milk
- Salt and freshly ground black pepper
How To Make White Onion Sauce
- Cook the Onion: Melt the butter in a small saucepan over high heat. Add the finely chopped onion and cook for 1 minute, stirring constantly. Reduce the heat, cover with a lid, and cook gently for about 20 minutes until the onion is soft but not browned.
- Make the Sauce Base: Sprinkle in the flour and stir well until it is fully combined with the onions.
- Add the Milk: Slowly pour in the hot milk, stirring continuously to prevent lumps. Keep stirring and bring the mixture to a gentle boil until the sauce thickens and becomes smooth.
- Season and Serve: Season with salt and freshly ground black pepper to taste. Serve hot on its own or poured over leeks, lamb, or mutton.
Recipe Tips
- For a smoother sauce, blend the mixture after cooking for an ultra-creamy texture.
- Want a richer flavor? Use half milk and half cream for extra richness.
- Pairing suggestions: This sauce works well with roast meats, steamed vegetables, or even mashed potatoes.
- To adjust consistency, add a little more milk if you prefer a thinner sauce.
How To Store & Reheat Leftovers
Storing in the Fridge: Keep in an airtight container in the fridge for up to 2 days.
Reheating on the Hob: Warm gently in a small saucepan over low heat, stirring well. Add a splash of milk if the sauce is too thick.
Can I Make White Onion Sauce Without Flour?
Yes, but the sauce won’t thicken as much. You can replace flour with cornflour (cornstarch) mixed with a little cold milk before adding it to the pan.
What Kind Of Onion Should I Use?
A medium white or yellow onion works best. Red onions are not recommended, as they will change the color and taste of the sauce.
What Is White Onion Sauce Used For?
White onion sauce is a classic British sauce that pairs well with lamb, mutton, leeks, roast meats, and even mashed potatoes. It adds a creamy, mild onion flavor to dishes.
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