Caramelized Onion and Welsh Scallion Pancakes

This traditional Welsh onion cake is a real classic. Layers of buttered potatoes, sweet caramelised onions and a tangy cheese centre make a comforting potato and onion bake that works beautifully as a hearty side or a simple vegetarian main.

It may not look like a sweet cake, and you’re right — it isn’t. Think of this Welsh onion cake as the Welsh cousin of dauphinoise potatoes: thinly sliced potatoes layered with gently caramelised onions then baked until tender and golden. Serve it with a Sunday roast, sausages, or add crispy fried bacon and turn it into a satisfying main course.

The main distinction from dauphinoise is the fat: where dauphinoise relies on cream, the Welsh onion cake uses butter. That butter gives the dish a nutty, golden flavour and helps create crisp edges and a tender interior. It’s an indulgence, but a delicious one.

Each potato layer is brushed with melted butter, seasoned with salt and pepper, and layered with soft caramelised onions. I add a layer of mature cheddar in the middle as a practical substitute for traditional Caerphilly. Cheddar melts well and brings a pleasant sharpness that balances the onions’ sweetness.

Baking brings everything together. The dish is covered for the first hour so the potatoes steam and soften, then uncovered for the final 15 minutes so the top browns and the edges crisp. When you turn it out, you get contrast — a crisp underside, soft buttery potato inside and nicely browned edges, with the melted cheese adding creaminess in the centre.

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Why you should try this Welsh onion cake

• Simple ingredients, big flavour – potatoes, onions, butter and cheese combine into a comforting, flavourful dish.
• Easy to prepare – slice, layer and bake; the oven does most of the work.
• Crispy and creamy in one bite – the mix of crisp edges, soft potato and gooey cheese is irresistible.
• Make-ahead friendly – it reheats well and leftover slices transform into excellent hash or fried potato cakes.

Recipe information

• ⌚ Prep time – 15 minutes
• ⌛ Cooking time – 75 minutes
• 🍚 Yield – serves 4 to 6 as a side dish

Ingredients for a Welsh onion cake

You can find the exact ingredient measurements in the printable recipe card at the end of this post.

• Potatoes – use an all-round variety such as Maris Piper or another waxy potato that holds its shape. Peel and slice very thinly (a mandolin helps).
• Onions – yellow, brown or white onions, peeled and thinly sliced.
• Butter – melted and brushed over each potato layer for flavour and browning.
• Cheese – mature cheddar works well as a substitute for traditional Caerphilly; grate it to scatter between layers. Omit if you prefer no cheese.
• Salt and ground black pepper – season each layer lightly so the finished dish is balanced.

Instructions

While the onions are cooking, peel and slice the potatoes as thinly and evenly as possible.

Remove the lid or foil and bake for a further 15 minutes until the top turns golden. Remove from the oven and let the dish rest for 10 minutes to help the layers settle.

Tips for a successful outcome

Top tips to ensure your Welsh onion cake turns out well every time.

• Slice potatoes thinly and consistently — about the thickness of a pound coin if possible.
• Cook onions slowly on low heat so they soften and lightly caramelise without going bitter.
• Lining the dish with parchment prevents sticking; if serving from the dish, simply butter it well to encourage browning.
• If you don’t have a lid, seal the dish tightly with foil to keep the steam in.
• Check doneness with a knife: if it meets resistance, return the dish to the oven a little longer before uncovering to brown.

Substitutions

Please check ingredients carefully if you have allergies or dietary restrictions.

• Vegetarian – the recipe is vegetarian; check cheese labels for animal rennet if required.
• Gluten-free – naturally gluten-free; verify packaged ingredients for cross-contamination.
• Dairy-free – use lactose-free butter and dairy-free cheese alternatives.
• Lower-fat – swap butter for olive oil for a lighter version; the result will be less rich but still tasty.

Variations

Ways to change the dish to suit your taste:

• Bacon – add layers of crispy fried bacon for a heartier bake.
• Leeks – swap onions for leeks to make a Welsh leek cake.
• Cheese – try Red Leicester, Gruyère or a mix of cheeses for different flavour profiles.
• Mini versions – assemble in ramekins or muffin tins for individual portions great for parties.

Equipment

Essential equipment for this recipe:

• Mandolin (or a sharp knife) for even thin slices.
• Frying pan with a lid to soften the onions gently.
• 9-inch round casserole dish (or similar size) for three layers of potatoes and two layers of onion.
• Spatula and pastry brush to butter the layers and help release the finished cake.

Storage and freezing

• Leftovers – store in an airtight container in the fridge for up to 3 days.
• Reheating – reheat in an ovenproof dish at 180°C/360°F for 15–20 minutes, removing foil for the last 5 minutes to crisp. Microwave reheating is possible but softens the texture.
• Freezing – bake in a disposable aluminium container, cool, wrap well and freeze for up to 3 months.
• Defrosting – thaw overnight in the fridge and reheat in the oven for best texture.

FAQ

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📋The recipe