Scandinavian food uses lots of foraged ingredients. For the filling try chanterelles or other wild or cultivated mushrooms. If using chanterelles or shiitake mushrooms, take off their woody stems and just use the caps.
shortcrust pastry 500g (an all-butter version will taste better)
soured cream 200g
Jarlsberg cheese 2 handfuls of grated
Fry the onion in a little butter until it is soft but not coloured. Tip onto a plate. Fry the mushrooms on a high heat in a little butter, stirring continually, until all the moisture has evaporated and they are quite dry. Mix in the cooked onion then cool the mixture. Season.
Roll the pastry out and use it to line a shallow springform cake tin, about 24cm diameter. The sides of the pastry should be about 4-5 cm, high enough to hold the mushroom filling. chill for 30 minutes and heat the oven to 200c/fan 180c/gas 6. Blind bake the pastry for about 15 minutes, or until it feels firm enough to hold its shape without collapsing, remove the paper and baking beans and cook for 5-10 minutes to dry out the base.
Fill the base with the mushroom mix. Mix ⅔ of the egg into the soured cream then pour over. Sprinkle the cheese over. Brush the pastry edges with the remaining egg and bake for about 30 minutes, or until the filling has set. Cool a little before removing from the tin.