In a large bowl, whisk together the eggs, milk, salt, and pepper.

Heat 1 tablespoon olive oil in a non-stick skillet over medium heat.

Add the chopped onion and sauté for 2-3 minutes, until softened.

Add the spinach leaves and cook for another 2 minutes, until wilted.

Remove the vegetables from the skillet and set aside.

Heat the remaining olive oil in the same skillet.

Pour the egg mixture into the skillet and cook for 2-3 minutes, until the edges start to set.

Sprinkle the shredded chicken and cooked vegetables evenly over the eggs.

Fold the omelette in half and cook for another 2-3 minutes, until the eggs are fully cooked and the filling is warm.

Serve hot and enjoy!