Jessie and Lennie Ware’s Jansson’s Temptation

This is Jessie and Lennie Ware's take on Jansson's Temptation, a traditional Swedish Christmas dish of creamy potatoes. It's richly comforting, and can be served as a side or a main.
From the book
Introduction
Ragnhild, my husband’s godmother (if agnostic socialists who lived in a feminist commune have such a title for their dearest friends), is a wonderful cook. She just couldn’t stay away from my mother-in-law Tessa after their Brixton commune days, so she found a house next door to her, with a direct passage to each other’s kitchen. One day, she passed this beloved Swedish winter classic over the garden wall. It is fundamentally a creamy potato gratin with fish. Ragnhild likes to make this with Swedish sprats, which confusingly are often sold with the word ‘ansjovis’ on the tin – but they are not the same as Mediterranean anchovies and have a milder, less salty flavour. We English philistines usually use anchovies. Don’t be put off by the anchovies – they melt away, but add such wonderful flavour. Perfect comfort food.
Ingredients
25g | unsalted butter, plus extra for greasing |
3 | large white onions, finely sliced into rings |
1kg | potatoes |
50g | tin anchovy fillets, drained and halved |
300ml | double cream |
150ml | whole milk |
A small handful of | crumbled crispbread or dried breadcrumbs |
Essential kit
You will need: a baking dish (about 1.5–2 litres capacity).
Method
Preheat the oven to 190°C/170°C fan/gas 5.
Heat the butter in a large heavy-based pan, add the onions and fry over a low heat for 15–20 minutes until soft and caramelised.
Meanwhile, peel the potatoes and cut into slim chip shapes, about 1–2cm wide.
Butter a baking dish (about 1.5–2 litres capacity). Layer the potatoes and onions in the dish, adding the anchovies among the layers.
Mix the cream and milk and pour over the potatoes: they should be almost covered. Scatter the crispbread or breadcrumbs over the top.
Cover with foil and bake for 50 minutes, then remove the foil and bake for a further 10 minutes. Serve hot.
Tip: White onions are better in terms of the appearance of this dish, although it doesn’t really matter.