In a boiling pot, add chicken, onion, garlic and salt and boil until chicken is cooked.
Drain, let cool and shred.
To assemble the tostada, chop tomatoes, lettuce and slice avocado in strips.
Spread 1 tbsp. of refried beans on tostada and sprinkle chicken on top.
Drizzle crema and top with lettuce, tomatoes and avocado slices.
Finish with a sprinkle of Cotija cheese and enjoy!