For the white sauce:
Mix all the ingredients together and keep stirring to avoid lumps.
Melt the butter add onions and stir-fry till they look glossy.
Add the mixed vegetables and continue to stir-fry over high heat till vegetables look like they are coated with the butter.
Take it off the heat and mix in the salt, pepper and white sauce.
Transfer mixture into an oven proof serving dish.
Sprinkle the cheese to cover the mixture, garnish with the tomato slices and bake in a pre-heated oven for half an hour, or till cheese is slightly brown.
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Key Ingredients: Butter, onion, salt, black pepper, tomato, all purpose flour, milk, cheddar cheese