Black bean, corn and fresh tomato salad with avocado sherry vinaigrette

Soak, cook and drain the black beans. Shuck the corn and cut the kernels off the cob. Halve the cherry tomatoes.

Peel, seed and dice the cucumber; dice the celery; chop the scallion.

Toss the black beans, corn, cucumber, celery, cherry tomatoes and green onions with the kosher salt and lime juice.

Cut the avocado at the last moment and put it straight into the blender with the sherry vinegar, which stops it colouring.

Add the olive oil, parsley, tarragon, garlic, shallot, Dijon mustard and water; puree until smooth.

Thin with more water and blend again to a pourable dressing.

Dress the salad with about two thirds of the vinaigrette and add the cheese.

Leave dressed 45 minutes to an hour to infuse.

To serve: spoon into a large leaf like a taco and garnish with halved cherry tomatoes and crumbled cheese.

Variation: line a whole wheat tortilla with the extra dressing, fill with the salad, roll it up and wrap it in plastic.