For the shortcrust pastry, put flour in a large bowl and mix with salt. Add the margarine, water and egg and use a mixer with a dough hook to make a shortcrust pastry. Wrap the finished dough in cling film and store in the refrigerator for half an hour.
For the filling, cut the bacon, onion and Gouda cheese into small cubes. Cut the mushrooms into 1/2 cm thick slices.
Heat some sunflower oil in a pan and fry the diced bacon in it. As soon as the bacon is crispy brown, add the onion and fry as well. Remove the bacon and onion mixture from the pan and fry the mushroom slices in the pan. Season the mushrooms with fish sauce, pepper and salt and fry until the mushrooms have evaporated. Finally add the chopped parsley and return the bacon and onion mixture to the pan with the mushrooms.
Grease a tart pan with margarine. Roll out the shortcrust pastry and place in the pan. Distribute the contents of the pan evenly on the dough and place the diced cheese on top.
Mix the crème fraîche with the eggs, add the mushroom processed cheese in small pieces and stir in.
Pour the topping over the mushroom topping and bake the cake in a preheated oven at 200 degrees top / bottom heat for about 30 minutes.