Put a kettle of water on to boil. Scrape the potatoes and put into a pot with the boiling water and some salt. Return to the boil and simmer for 15–20 minutes or until the potatoes are tender.
Halve and seed the capsicum, slice into strips and put into a salad bowl. Trim the celery; reserve the leaves for a garnish and finely slice the rest. Add to the capsicum. Peel the onion, halve lengthways and slice lengthways again into crescents. Add to the bowl.
To make the dressing, mix the mayonnaise and mustard in a small bowl and add Tabasco to taste.
Drain the potatoes, cool under cold running water, drain again and add to the salad. Spoon in the dressing, grind pepper over the top and mix well. Garnish the salad with celery leaves.
Add chopped hard-boiled eggs to the salad to turn it into a meal.