Pour boiling water over the atsuage to remove the excess oil. Cut the green pepper and carrot into matchsticks. Thinly slice the onion.
Heat the vegetable oil in a frying pan and stir-fry the vegetables. When they become tender, add the dashi stock and seasonings and bring to a boil.
Mix together the ingredients and gradually add a little at a time to the vegetables to thicken the sauce. The sweet and sour sauce is ready!
Toast both sides of the atsuage, each for about 3 minutes, in a toaster oven. The water will evaporate from the surface, so it should become crispy. It's ready when the surface is lightly browned!
Cut the atsuage from Step 4 into large, bite-sized pieces and transfer to a plate. Top with the sauce from Step 3 and enjoy!