If you’ve ever wished mashed potatoes could secretly be dessert and still work as a side dish, imelletty perunalaatikko is exactly that kind of magic.
This traditional Finnish malted potato casserole is a star of the Christmas table (joulupöytä), sharing the spotlight with carrot and rutabaga casseroles, ham, gravlax and all the usual Nordic suspects.
Unlike most potato bakes, this one is naturally sweetened: you mash potatoes, mix in wheat flour and keep the mash gently warm so the enzymes in the flour break some of the potato starch into sugars. Later you add milk, butter, bake it for hours, and end up with a soft, caramel-coloured casserole that tastes a bit like a mash-up of mashed potatoes and a very restrained custard.
Think comfort food meets food science experiment. Flavour-wise it’s closer to a barely sweet pumpkin or sweet potato casserole than to anything savoury and garlicky.
What Is Imelletty Perunalaatikko, Exactly?
The name breaks down like this:
- Imelletty = sweetened/malted (by enzymes, not sugar dumped in)
- Peruna = potato
- Laatikko = “box” → casserole
The dish originates from the Päijät-Häme region of Finland and is built from just a handful of ingredients: potatoes, wheat flour, milk and butter, with optional dark syrup for extra sweetness.
The defining step is the sweetening phase:
- You mash cooked potatoes.
- You mix in wheat flour while the mash is warm – around 50 °C / 122 °F.
- You keep it at that gentle temperature for several hours so the amylase enzymes in the flour can convert potato starch into natural sugars.
If the sweetening doesn’t go quite far enough, modern recipes simply boost the sweetness with a little dark syrup, which has a molasses-like flavour and is very common in Finnish baking.
A Quick Science Note (for Food Nerds)
Wheat flour contains amylase, an enzyme that snips large starch molecules into shorter sugar chains.
The enzyme is happy and active in a warm mash (roughly 50–65 °C / 122–149 °F); above about 75 °C / 167 °F it starts to break down and stop working.
That’s why Finnish recipes talk so much about temperature and time. The sweet flavour is literally built inside the potato purée.
You don’t need lab gear for this – just a reasonably warm, safe spot and ideally a thermometer.
Imelletty Perunalaatikko – Finnish Sweetened Potato Casserole
Ingredients
Method
- Peel the potatoes and cut into chunks of roughly equal size.
- Place in a large pot, cover with unsalted water and boil until very tender.
- Drain well, reserving a little of the cooking water if you like for adjusting consistency.
- Mash until completely smooth – a potato ricer is ideal for a silky casserole.
- You want a soft mash, but not too runny. Add a splash of the cooking water if it seems dry.
- Let the mash cool down a little until it’s warm but not hot – ideally around 50 °C / 122 °F.
- Stir in half of the flour (1 dl) and about half of the butter, cut into small pieces.
- Mix thoroughly, then sprinkle the remaining flour on top of the mash without stirring it in completely – this gives the enzymes a good contact layer.
- Cover the pot with a lid.
- Keep the mash warm (roughly 50–65 °C / 122–149 °F) for 4–8 hours.
- If you have a thermometer, check occasionally to make sure it doesn’t climb much above 70 °C / 158 °F.
- Over time, the mash will become looser and noticeably sweeter and more mellow in flavour. The top may darken slightly where the flour sat – that’s normal.
- Once you’re happy with the sweetness, stir the mash thoroughly so any flour on top is fully mixed in.
- Warm the milk and melt the rest of the butter.
- Add milk gradually, stirring, until the mash is softer than normal mashed potatoes, but not soupy – think thick cake batter.
- Season with salt and nutmeg/white pepper (if using).
- Taste. If the sweetening hasn’t developed enough, add 1–2 tbsp dark syrup and stir well. The flavour should be gently sweet, not dessert-level sugar bomb.
- Preheat the oven to 150 °C / 300 °F.
- Grease one large or two medium casserole dishes with butter.
- Pour the potato mixture into the dishes, leaving some headspace – the casserole will bubble and puff a little.
- Dot the surface with a few small bits of butter. You can also draw a simple pattern with a spoon or fork for the classic Finnish look.
- Bake for 2–3 hours, until the top is deep golden brown, the edges have caramelised a bit and the casserole feels set in the centre..
- Let it rest at least 15 minutes before serving so it firms up slightly.
How to Serve Imelletty Perunalaatikko
On a Finnish Christmas table, this casserole is usually served:
- Alongside Christmas ham,
- with other casseroles – carrot (porkkanalaatikko) and rutabaga (lanttulaatikko) –
- plus rosolli beetroot salad, gravlax and pickled herring.
Other serving ideas:
- As a holiday side with roast turkey, chicken or pork.
- With a green salad and roasted Brussels sprouts for a vegetarian or flexitarian Christmas plate.
- As a cosy Sunday winter side with anything roasted – it reheats beautifully.
Variations & Twists
To fit different kitchens and diets:
- Make-ahead / freezing: You can assemble the casserole the day before and keep it chilled, or bake it fully and reheat gently. Some Finnish home cooks freeze unbaked casseroles and bake them on Christmas Eve.
- Dairy-free: Use oat or soy milk and a neutral oil or vegan butter. The sweetening step relies on flour enzymes, not dairy, so it still works.
- Slightly richer: Replace part of the milk with cream for an extra luxurious holiday version.
- Shortcut sweetness: If you don’t want to fuss too much with temperature control, you can still do a shorter sweetening step and rely a bit more on dark syrup for flavour.