Fry the pork belly until golden and crispy in the same pan the omelette will be cooked in.

Place the prepared pork belly in an ovenproof dish and keep it warm in the oven at 100 degrees Celsius (212 degrees Fahrenheit) until the omelette is ready.

Whisk the egg whites until slightly stiff, then set aside.

Cut the potato into smaller pieces and add them to the pan with the pork belly fat.

In another bowl, whisk eggs, milk, and flour until smooth. Add pepper and salt (salt can be omitted if the pork belly is very salty).

Gently fold the slightly stiff egg whites into the omelette mixture.

Pour the egg mixture over the potatoes and stir gently until the egg mixture starts to set.

Let the omelette bake further over medium heat for about 30-45 minutes, checking regularly to ensure it doesn't burn at the bottom. When the omelette feels firm, it is ready to serve.

Garnish the omelette with pork belly, tomatoes, and optionally chives.

It can also be served with a bit of homemade rye bread and homemade butter.