Prepare the vegetables: Wash and slice zucchini (half-inch strips) and mushrooms (thin slices). Chop spring onions.
Make the batter: In a large bowl, mix flour with cold water to create a thin batter.
Saute the vegetables: Heat oil in a pan over medium-high. Sauté zucchini and mushrooms until tender, then add spring onions and sweetcorn for an additional 2 minutes.
Cook the pancake: Combine cooked vegetables with the batter. In the same pan, add a thin layer of batter and cook for 3-5 minutes on one side, then flip and cook for 2 minutes on the other side, pressing down with a spatula to keep it thin.