in large bowl, combine sourdough discard, egg, soy sauce, and a pinch of salt. mix well with fork or whisk until it becomes a batter like consistency.
add in shredded vegetables. toss until vegetables are coated in batter.
heat up oil on a skillet on med-high heat. when oil is sizzling hot, spoon in mixture and flatten to form in the shape of a pancake.
cover and cook for 3-4 minutes, or until bottom is golden brown. flip, using a spatula or a lid, and continue cook for another 3-4 minutes, uncovered. okonomiyaki is done when both sides are crispy and golden brown.
serve immediately, while warm, on a plate with toppings of your choice. i like to drizzle mayo (preferably kewpie) and hoison sauce, and top with sesame seeds, scallions, and lao gan ma chili crisp.