French Onion Mashed Potatoes

Oh, Mondays! After ferrying the little ones to school and tackling the mountain of laundry, a bit of comfort food is just what the doctor ordered. And whilst plain mashed potatoes are alright, these French Onion Mashed Potatoes? They’re in a different league. I’ve been making this variation for years, ever since I tried to recreate a fancy restaurant side dish, and honestly, it’s become a firm family favourite. The sweet caramelised onions blended with creamy mashed potatoes…it’s pure magic. I promise you, even your pickiest eaters (ahem, my Thomas!) will be asking for seconds. This recipe delivers unbelievably flavourful and comforting mashed potatoes with a touch of French flair – perfect for a midweek treat or a Sunday roast accompaniment.

Why This Recipe Works

As a busy mum, I completely understand the need for quick, easy, and delicious recipes. This French Onion Mashed Potatoes recipe ticks all the boxes. Over my 8+ years of home cooking, I’ve learned to streamline recipes without sacrificing flavour. This recipe is:

• Straightforward: It uses simple ingredients and a no-fuss method.
• Child-Approved: The sweetness of the caramelised onions is a real hit with kids.
• Versatile: Perfect as a side dish or even as a topping for shepherd’s pie.

The most challenging part is patiently caramelising the onions, but trust me, it’s worth the effort. And even if you rush it a bit (we all have those days!), it will still be delicious.

Ingredients

• 1 kg potatoes, peeled and quartered (Maris Piper or King Edward are best)
• 2 large onions, thinly sliced
• 50g butter
• 2 tbsp olive oil
• 100ml milk
• 50ml double cream
• 1 tsp dried thyme
• Salt and freshly ground black pepper to taste

Ingredient Notes

Potatoes: Maris Piper or King Edward potatoes are ideal for mash as they are floury and absorb the flavour well. If you can’t find these, any good mashing potato will do.

Onions: White or yellow onions work well. Don’t be tempted to use red onions, as the flavour profile isn’t quite right for this dish.

Thyme: Dried thyme adds a lovely earthy note. Fresh thyme is lovely too, use about 1 tablespoon of chopped fresh thyme leaves.

Cream: Double cream adds richness, but you can substitute it with single cream or even more milk for a lighter version. I’ve even used crème fraîche in a pinch

Step-by-Step Instructions

Step 1: Prepare the Potatoes. Place the potatoes in a large saucepan and cover with cold water. Add a pinch of salt and bring to a boil. Reduce the heat and simmer for 15-20 minutes, or until the potatoes are tender and easily pierced with a fork. Remember to check them; nobody likes a lumpy mash!

Step 2: Caramelise the Onions. While the potatoes are cooking, melt the butter and olive oil in a large frying pan over medium-low heat. Add the sliced onions and thyme. Cook slowly, stirring occasionally, for 30-40 minutes, or until the onions are deeply golden brown and caramelised. This requires patience, but the flavour payoff is huge. They should be soft and sweet, not burnt. Through trial and error, I’ve learned that low and slow is the way to go!

Step 3: Drain the Potatoes. Once the potatoes are cooked, drain them well in a colander. Return them to the saucepan.

Step 4: Mash the Potatoes. Add the milk and cream to the potatoes. Mash with a potato masher until smooth and creamy. You can use an electric mixer for an extra smooth mash, but I find a good old-fashioned masher does the trick perfectly well. My children prefer a slightly chunkier mash, so I don’t overdo it.

Step 5: Combine and Season. Stir the caramelised onions into the mashed potatoes. Season with salt and freshly ground black pepper to taste. Give it a good mix to ensure the onions are evenly distributed throughout the mash. Have a taste and adjust the seasoning as needed. Remember, a little seasoning can go a long way.

Step 6: Serve. Serve the French Onion Mashed Potatoes hot and enjoy! Garnish with a sprinkle of fresh thyme or a pat of butter, if desired.

My Kitchen Tips & Tricks

• Prevent Sticking: To prevent the onions from sticking to the pan while caramelising, add a tablespoon of water every now and then.
• Speed Up Caramelisation: A pinch of sugar can help speed up the caramelisation process, but don’t overdo it!
• Make-Ahead Tip: You can caramelise the onions ahead of time and store them in the fridge for up to 2 days. This saves valuable time on busy weeknights.
• Child-Friendly Adjustment: If your children are hesitant about onions, chop them very finely or even blend a portion of the caramelised onions into a purée before adding them to the mash.
• Texture Tip: For extra smooth mashed potatoes, pass them through a potato ricer before adding the milk and cream.
• Flavour Boost: Add a clove of crushed garlic to the onions during the last 10 minutes of caramelising for an extra layer of flavour.
• Butter Matters: Use a good quality butter for the best flavour. It really makes a difference!

Storage & Meal Prep

Storage: Store leftover French Onion Mashed Potatoes in an airtight container in the refrigerator for up to 3 days.

Reheating: Reheat in the microwave or in a saucepan over low heat, adding a splash of milk or cream to loosen the mash if needed. Be sure to stir frequently to prevent sticking.

Make-Ahead: You can prepare the mashed potatoes and caramelised onions separately up to 2 days in advance. Store them in the refrigerator in airtight containers. When ready to serve, reheat both and combine.

Batch Cooking: This recipe doubles or triples easily, making it perfect for batch cooking and freezing. Allow the mashed potatoes to cool completely before transferring them to freezer-safe containers. They can be frozen for up to 2 months. Thaw overnight in the refrigerator before reheating.

Substitutions & Variations

Dairy-Free: Use plant-based milk and cream alternatives, along with a dairy-free butter substitute. I’ve found oat milk works particularly well.

Gluten-Free: This recipe is naturally gluten-free.

Vegetarian: This recipe is suitable for vegetarians.

Herb Variations: Try using different herbs, such as rosemary or sage, instead of thyme. A sprinkle of chopped chives adds a fresh, vibrant flavour.

Cheese: For an extra indulgent twist, stir in some grated Gruyère or Parmesan cheese just before serving. It melts beautifully into the warm mash.

Frequently Asked Questions

Can I prepare this the night before?

Absolutely. In fact, I often caramelise the onions the day before to save time. Store them in an airtight container in the fridge and simply reheat them when you’re ready to make the mash. You can also mash the potatoes ahead of time, but they may require a splash of extra milk or cream when reheating to restore their creamy texture.

How do I know when the onions are properly caramelised?

The onions should be a deep golden brown colour and very soft and sweet. They should have reduced significantly in volume. Patience is key; don’t rush the process, or they will burn rather than caramelise.

Can I use different types of potatoes?

While Maris Piper or King Edward potatoes are my preferred choice, any good mashing potato will work. Avoid waxy potatoes, as they don’t mash as well.

My mashed potatoes are too dry. What can I do?

Add a little more milk or cream until you reach your desired consistency. You can also add a knob of butter for extra richness.

Can I freeze leftover French Onion Mashed Potatoes?

Yes, you can freeze them. Allow the mashed potatoes to cool completely before transferring them to freezer-safe containers. They can be frozen for up to 2 months. Thaw overnight in the refrigerator before reheating.

Will my children like this?

My Thomas is usually a bit fussy, but he loves these! The sweetness of the caramelised onions makes them surprisingly appealing to children. You can always adjust the amount of onions to suit their taste.

Can I add garlic?

Absolutely! Garlic adds a lovely depth of flavour. Add a clove or two of crushed garlic to the onions during the last 10 minutes of caramelising.

Serving Suggestions

These French Onion Mashed Potatoes are delicious served alongside:

• Roast chicken or beef
• Sausages and gravy
• Shepherd’s pie (as a topping)
• Grilled fish
• Vegetarian sausages

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