Make salty puff pastry in a food processor using chopper. It’s only a matter of pressing the pulse button a couple of times until all the ingredients join (flour, butter, salt and yolk). Then add one tbsp of water at first, and if the dough seems to be too dry, add another one.
Roll the dough between two pieces of cling film or baking paper. This way you won’t need to use any more flour underneath the dough. Move the dough on a baking pan (with detachable bottom) and poke with fork. Put the corpus into a fridge at least for half an hour.
Beat eggs with white yogurt and grated emmental. Keep part of the cheese for final scattering. Add diced dried ham or bacon and red onion. Season with salt and pepper.
Bake cooled corpus at 200 degrees for 10 minutes. It isn’t right to bake it “blindly”.
Then spread the remaining egg white over the corpus. Bake for 1-2 more minutes. This will create some impermeable layer and the filling will not soak into the dough during baking, so the pastry stays crunchy.
In the end, pour the mixture into the baked pastry and bake for 20 minutes more. Scatter the remaining cheese over the top before baking.
If you fancy a vegetarian version of this cake, replace dried ham by spring onion, herbs or olives. Emmental cheese can be replaced by any other cheese, for example more intense cheddar, or parmesan. Or you can make your own mixture of cheeses, which you prefer.
I used thick white greek yogurt. But use any other which you like and are used to.
Something else ?