This Mary Berry-inspired onion sauce is a comforting British classic made with gently softened onions and a creamy white sauce. It has a smooth, silky base with tender pieces of onion and a mellow, savoury flavour. The recipe is easy enough for beginners and takes about 35 minutes from start to finish. Serve it warm with roast meats, sausages or vegetables.
Ingredients
For the Onion Sauce
- 2 medium onions, about 300g, peeled and finely chopped
- 30g unsalted butter
- 30g plain flour
- 500ml whole milk
- ¼ teaspoon fine salt, plus more to taste
- ¼ teaspoon freshly ground black pepper
- A small pinch of freshly grated nutmeg, optional
How to Make Mary Berry-Inspired Onion Sauce
This sauce is made entirely on the hob, so there is no need to heat the oven.
- Soften the onions: Melt the butter in a medium saucepan over low heat. Add the chopped onions and cook gently for 12 to 15 minutes, stirring occasionally, until soft and translucent. Do not let them brown.
- Add the flour: Stir the flour into the onions until no dry patches remain. Cook for 1 minute, stirring constantly, to remove the raw flour taste.
- Mix in the milk: Gradually add the milk, a little at a time, stirring well after each addition. The mixture will be thick at first but will loosen as you add the remaining milk.
- Simmer the sauce: Bring the sauce to a gentle simmer over medium-low heat, stirring frequently. Cook for 5 to 8 minutes, until thick enough to coat the back of a spoon and the onions are completely tender.
- Season and serve: Stir in the salt, pepper and nutmeg, if using. Taste and adjust the seasoning, then spoon the sauce into a warmed serving jug or serve directly from the pan.
Tips for the Best Onion Sauce
How Do I Keep the Onions Sweet and Mild?
Cook the onions slowly over low heat until they are soft but not coloured. Browning gives them a deeper, sweeter flavour, which is delicious but less traditional in a creamy onion sauce.
How Can I Prevent Lumps?
Add the milk gradually and stir thoroughly between additions. If small flour lumps remain, whisk the sauce well as it warms. For a completely smooth sauce, blend it carefully once the onions are tender.
What Should I Do if the Sauce Is Too Thick?
Stir in a splash of milk at a time until the sauce reaches your preferred consistency. Let it warm through again before serving.
How Can I Thicken a Thin Onion Sauce?
Simmer it gently for a few more minutes, stirring often. The sauce will also thicken slightly as it cools.
Serving Suggestions
- Spoon over roast chicken or turkey.
- Serve with sausages and creamy mashed potatoes.
- Pair with roast pork and steamed greens.
- Pour over cauliflower, leeks or roasted root vegetables.
Storage and Reheating
Room Temperature
Do not store onion sauce at room temperature. Cool it promptly and refrigerate within 2 hours of cooking.
Refrigerator
Transfer the cooled sauce to an airtight container and refrigerate for up to 3 days. Reheat gently in a saucepan until piping hot throughout, stirring often and adding a splash of milk if needed.
Freezing
Freeze cooled sauce in a freezer-safe container for up to 2 months. Thaw overnight in the refrigerator, then reheat until piping hot, stirring well. The sauce may separate slightly after freezing, but whisking and a little milk can help bring it back together.
Nutrition
Approximate values per serving, based on 6 servings:
- Calories: 120 kcal
- Carbohydrates: 13g
- Protein: 4g
- Fat: 6g
- Saturated fat: 4g
- Sodium: 140mg
Nutrition values are estimates and will vary with ingredients and portion sizes.
FAQs
Can I make onion sauce ahead of time?
Yes. Make it up to 3 days ahead, cool promptly and refrigerate in an airtight container. Reheat gently until piping hot, adding a little milk if it has thickened.
Can I make onion sauce without dairy?
Yes. Use a dairy-free butter alternative and an unsweetened plant-based milk. Oat or soya milk generally gives a creamy result, although the flavour will differ slightly.
Can I make this onion sauce gluten-free?
You can use a gluten-free plain flour blend in place of the plain flour. Check the sauce as it simmers, as different blends may thicken at different rates.
Should onion sauce be smooth or chunky?
Traditionally, onion sauce can have soft pieces of onion throughout. For a smoother finish, blend the cooked sauce carefully until it reaches your preferred texture.
What onions are best for onion sauce?
Ordinary yellow or white onions work well. Chop them finely and cook them gently for a mild, sweet flavour.
Creamy Onion Sauce
Course: SauceCuisine: BritishDifficulty: Easy4
servings30
minutes40
minutes300
kcal1
hour10
minutesA Mary Berry-inspired British onion sauce with tender onions and a creamy white sauce, ready in 35 minutes.
Ingredients
2 medium onions, about 300g, peeled and finely chopped
30g unsalted butter
30g plain flour
500ml whole milk
¼ teaspoon fine salt, plus more to taste
¼ teaspoon freshly ground black pepper
A small pinch of freshly grated nutmeg, optional
Directions
- Melt the butter in a medium saucepan over low heat. Add the onions and cook gently for 12 to 15 minutes, stirring occasionally, until soft and translucent but not browned.
- Stir in the flour and cook for 1 minute, stirring constantly.
- Gradually add the milk, stirring well after each addition until combined.
- Bring to a gentle simmer over medium-low heat. Cook for 5 to 8 minutes, stirring frequently, until the sauce thickens and the onions are tender.
- Stir in the salt, pepper and optional nutmeg. Taste, adjust the seasoning and serve warm.
Notes
- Keep the heat low while softening the onions so they do not brown.
- Add a splash of milk if the sauce becomes too thick.
- Refrigerate cooled sauce for up to 3 days or freeze for up to 2 months.
