Rinse the chicken breast fillets in cold water, then dry and cut into approximately 1 cm dice. Heat the peanut oil in a frying pan and quickly sauté the chicken. Season with salt, pepper and chili powder, then leave to cool slightly.
Drain the red kidney beans. Wash the lettuce, spin dry and shred. Peel and halve the avocados and remove the stones, then mash the flesh with a fork. Season with salt and pepper and mix in the lemon juice.
Heat a dry frying pan and quickly toast the tortillas on both sides. Spread immediately with the avocado puree then scatter evenly with iceberg lettuce, chicken and red kidney beans. Roll up and serve immediately.