1. An infallible method is to make a vegie pattie - combine shredded or finely chopped raw vegetables with a little cornflour or plain flour, a little milk and beaten egg, then fry in little oil.
2. Vegetables pureed are also yummy, looks like potato puree.
3. A nice white sauce hiding the vegies is good.
4. Lastly there are soy sauce mixes, mild mustard/mayo and sweet chilli sauces
you could douse it in.
Good luck, make sure you enjoy eating these at the same time, too!!