1) Line a round back tin with the shortcrust pastry and let it rest in the fridge.
2) Meanwhile, heat up the butter in a large pot. Add the finely sliced onions and cook them for gently, covered, for 10 minutes. Then add the flour, stir well and add the cold milk. Bring back to the boil, stirring all the time, season with salt, pepper and some nutmeg.
3) Let this onion mixture cool down and add 3 egg yolks mixed with the cream in it.
4) Start the oven at 210'C (gas mark 7 or 410'F).
5) Whisk the egg whites until stiff and carefully fold them into the onion mixture.
6) Blanch the pork belly dices and cool them down. Place them onto the shortcrust pastry. Then, carefully pour the onion mix into the shell and smooth the top of the mixture with a spatula. Bake for 30 minutes in the middle of the oven.
credits photo : © alain wacquier