Peel and core the apples and cut the flesh into chunks. Put these in a large saucepan with the caster sugar and 3 tbsp water and cook over a gentle heat until the apples are completely tender. Stir every so often and mash the fruit down roughly with the back of a wooden spoon. The finished purée shouldn’t be too wet – if it is, simmer it over a low heat until it reduces and loses some of its moisture.
Check the apples for sweetness – they shouldn't be too sweet as it's being mixed with sweet cream and breadcrumbs – and tip into a bowl to cool. In Scandinavia, the stewed apples are usually puréed until smooth, but you can also keep them chunky.
Melt half the butter in a frying pan and add the brown breadcrumbs and half the brown sugar. Sauté, stirring constantly, over a medium heat until the breadcrumbs are golden. Add half the cinnamon and half the cardamom and continue to cook for about 1 min. Spread out on a tray – it cools quicker this way – and leave until it’s room temperature. Do the same with the rye breadcrumbs, then mix the breadcrumbs together in a bowl.
Whip the cream, adding the icing sugar and the lemon (add the lemon before the cream is too thick as the acid in the lemon has a thickening effect). If you are going to add the aquavit, do it once the cream has been whipped.
Layer the apples, breadcrumbs and whipped cream in a glass bowl (so you can see the layers) starting with the stewed apples and ending with a layer of cream. Scatter over the hazelnuts just before serving.