Heat oil in a pan over medium-low heat. Add chopped garlic and fry till it is golden in colour.
Add the chicken cubes, salt and pepper. Saute for 4-5 minutes until fully cooked. Turn the heat off and transfer it to a plate.
In a large mixing bowl, add eggs, salt and pepper.
Beat the eggs with a whisk until its pale yellow in colour.
Add the chopped onion, capsicum, green chillies and tomatoes. But don't pour all of it. Keep aside 2 tbsp of each vegetable for later use. Then add milk and mix everything nicely.
Heat the same pan in which the chicken was sauteed. We will use the leftover garlic flavoured oil in the pan to cook the omelette. This will give a nice aroma to the dish. Lower the flame and pour in the egg mixture.
Cover it with a lid and cook on low flame for 5 minutes.
Sprinkle some chopped tomato, capsicum, onion and green chillies on one side of the omelette. Then sprinkle garlic chicken over it.
Add the grated mozzarella cheese evenly over the chicken filling.
Fold the omelette in half and again cover with a lid. Cook for 1-2 minutes. Carefully flip the omelette and again cover with a lid. Cook for a few minutes and then remove from heat.
Slide it to a plate and serve immediately.