heat oil in a wok or kadai.
add the chopped ginger and garlic and stir fry on high flame for half a minute.
then add the onions and stir fry for 2-3 minutes on a high flame.
add the bell pepper and mushrooms and stir fry for 2-3 minutes.
then add the blanched veggies - cauliflower, french beans and carrots and stir fry for another 2-3 minutes.
add the celery and stir fry for a minute. in a small bowl, mix the soy sauce and tomato sauce.
add these two sauces to the veggies. stir and season with pepper, sugar and salt.
stir and add 2 cups of water or veg stock.
let the sauce get heated through and come to a simmer.
dissolve the 2 tbsp corn starch with 1/2 cup water to a smooth paste
add the corn starch paste to the veggies and stir briskly so that no lumps are formed.
simmer till the corn starch gets cooked in the sauce and the sauce thickens.
lastly add the apple cider or vinegar.
stir through and serve sweet and sour vegetables hot with veg fried rice or steamed rice or plain noodles.