Place the tempeh in a medium pan and cover with about ¼ cup (60ml) water. Cover with a lid and steam for 10 minutes.
Meanwhile, prepare the breadcrumbs by mixing all the breading ingredients EXCEPT the flour together in a medium dish. Big enough to fit the cutlet in.
Once the tempeh is done steaming drain any additional water if it is left. Add it into a food processor with the drained chickpeas, nutritional yeast, egg replacer and seasonings. Pulse for a few minutes until everything is broken down and you are able to form a ball with the mixture.
Divide the mixture into 4 to make 4 cutlets or however many cutlets you want but I wouldn't do more than 6 as they will be quite small.
Take one ball of the mixture and use clean hands to flatten it. It may help if your hands are wet. Make it thin but not too thin that it will break. If you need help watch the YouTube video. Dip the cutlet into flour and flip on both sides. Then use a spatula to help to move it into the aquafaba (chickpea brine). I found it was important to do this part quickly and use the spatula to help support the cutlet. Finally, dip both sides in the breadcrumbs and then place on a lined baking sheet. Repeat until all cutlets are coated.
Cover with spray oil if you like and bake at 400℉ (204℃) for 20 minutes or until crispy.
To assemble the sandwich spread the vegan mayo over the bread. Add the cutlet, if you like add a sprinkle of salt. Then add the lettuce and top piece of bread and enjoy.