Prepare all ingredients: eggs, ketchup, ham, onion, and mozzarella cheese.

Dice the ham into small cubes and chop the onion if using.

Heat a pan with a small amount of oil and sauté the ham and onion until lightly browned.

Add ketchup to the pan and stir well to coat the ham and onion. Remove the mixture and set aside.

Beat the eggs with a pinch of salt and strain through a sieve to remove lumps and air bubbles.

Heat a pan with a thin layer of oil and wipe with a paper towel to create a non-stick surface.

Pour the egg mixture into the pan and cook gently, stirring occasionally to create soft scrambled eggs.

When the eggs are 70% cooked, turn off the heat and add the ham mixture and mozzarella cheese on top.

Fold the omelette carefully by tilting the pan and using a spatula or chopsticks to shape it into a neat oval.

Cook on the lowest heat to seal the edges and ensure the cheese melts inside.