Preheat the oven to 220 degrees C. If you have a pizza stone, place it in the oven while it preheats.
In a food processor, combine the avocados, garlic and coriander. Puree while adding lime juice and salt to taste. Cover and set aside.
Brush both sides of the bases with olive oil. Spread the avocado mixture thickly over the top of each base, then sprinkle with Mozzarella chesse. Arrange the chicken and tomato on top. Sprinkle with cheddar cheese.
Place pizzas on a baking tray if you do not have a pizza stone. Cook for 10 minutes in the preheated oven.