Watercress and mixed vegetable salad

This is a salad using Watercress as the basis. The recipe for this salad contains a good selection of seasonal vegetables and the dressing with whole grain mustard is sharp and spicy.
Ingredients
Watercress, washed and chopped and put as the base layer.
6 Chinese leaves washed and chopped fine.
1 red onion diced very fine
4 tomatoes diced fine.
I like to arrange my salads as above so they are pleasing to the eye.
Chilli Salad Dressing
1 tablespoon of olive oil
1 tablespoon of red or white wine vinegar
1 teaspoon of grained mustard
1/2 a fresh chilli chopped very fine
salt and pepper
1/2 teaspoon of granulated sugar
Mix everything together.
This dressing is like sweet and sour with a zap of hot chilli.
I serve as a starter or with Steak or chicken.