Wash the bok choy thoroughly and cut into bite-sized pieces.
Prepare the tortilla and place it in a round baking mold.
Mix eggs, milk, and salt to make the quiche filling.
Place bok choy, bell pepper, onion, and other vegetables on top of the tortilla.
Pour the quiche filling over the vegetables.
Sprinkle mozzarella cheese evenly on top.
Preheat the oven to 180°C and bake for 25 minutes.