Put the corn starch in a medium bowl.
Whisk in the vegetable stock until it dissolves.
Stir in the soy sauce, Madeira or sherry, dried ginger (If using - fresh ginger should be added to the vegetables later), and pepper. Set aside.
Put the vegetable oil and the sesame oil in a large non-stick wok or frying pan and heat over medium high heat.
Stir in the sliced red onions, garlic, fresh ginger (if using) and chopped chilis (if using).
Add the carrots and stir fry for a minute or two.
Now add the mushrooms, red and yellow peppers, and zucchini (if using).
Stir fry for 2 or 3 minutes, until tender crisp.
If using snow peas, stir them in now, along with the cashews.
Stir the sauce mixture and then add it to the wok, stirring and tossing with the vegetables.
When the sauce thickens, stir in the sliced scallions. If the sauce becomes to thick, stir in a little freshly boiled water from the kettle to give a better consistency.
Serve in warmed bowls either as is, or over cooked rice or noodles (for gluten free be sure the noodles are suitable).