Prepare the vegetables: Finely chop 200 grams of lettuce, 1 medium-sized carrot, 1 small cabbage, 1 medium-sized onion, and 1 small capsicum.

In a pan, heat 2 tablespoons of oil over medium heat. Add the chopped onion and sauté until translucent.

Add the chopped carrot, cabbage, and capsicum to the pan. Cook for 5-7 minutes, stirring occasionally, until the vegetables are tender.

Add the chopped lettuce, 1 teaspoon of soy sauce, 1/2 teaspoon of black pepper powder, and salt to taste. Cook for another 2-3 minutes, then remove from heat and let the mixture cool.

Place a spring roll wrapper on a flat surface. Place 2 tablespoons of the vegetable mixture on one corner of the wrapper. Fold the corner over the filling, then fold in the sides and roll tightly. Seal the edge with a mixture of 1 tablespoon of cornflour and 2 tablespoons of water.

Heat oil in a deep frying pan over medium heat. Fry the spring rolls in batches until golden brown and crispy, turning occasionally to ensure even cooking. Remove from oil and drain on paper towels.

Serve the vegetable spring rolls hot with sweet chili sauce or tomato ketchup.