Put all the ingredients for the bread in a bowl. Whisk together until homogeneous and smooth.
Pour the batter into a greased muffin cup or small baking pan.
Microwave for 90 seconds. Transfer to a cutting board to cool for 90 seconds before cutting into slices.
MAKING THE FILLINGS
Prepare the boiled chicken breast and shred it.
Pour the oil into a hot frying pan. Throw in the chicken pieces and sauté with onion. Add a decent amount of salt and pepper to flavor. Allow cooking for 10 minutes.
Mash the avocado in a small bowl.
Lay the bread on a plate. Spread the mashed avocado on one piece and the cooked chicken mix in another. Sandwich the pieces together. Do the same for the remaining pieces of bread.