Begin with the pastry. Mix both flours and the salt together in a large bowl then rub in the butter with your fingertips. Mix in the quark, or fromage frais. Knead the dough lightly with your hands just until the ingredients are amalgamated. Or just put everything in a food processor and pulse-blend it together. In both cases, if the dough does not come together, sprinkle in a little water. Roll the dough out on a floured surface and butter a 28 cm (ish) pie dish. Use the pastry to line the dish, then leave to rest in the refrigerator for one hour.
Preheat the oven to 200C/400F/gas mark 5. Cover the pastry case with baking parchment and pour in some dried beans or raw rice to weigh it down. Blind bake in the hot oven for 15 minutes. Remove the paper and beans and bake for five minutes more. Meanwhile, make the filling: cut the spring onion into two centimetre pieces, cut asparagus into pieces of two centimetre, discarding of the bottom pieces. Sauté the spring onions in olive oil for five minutes, without browning. Let them drain in a colander if necessary.
Beat the eggs in a large mixing bowl, and then fold in the creme fraiche and nutmeg, with a wooden spoon. Now add the spring onion and asparagus and Castello Danish Blue and mix again. Season to taste with salt and pepper. Pour the mixture into the blind-baked pastry case and return to the oven to bake for 35-40 minutes, or until the filling has set. Serve with green salad or wilted spinach.