Warm the vinegar with the sugar and salt and stir until dissolved. Bring up to the boil then pour over the onions and radishes. Leave to steep and cool for at least 15 minutes.
To make the filling, heat the oil in a pan, add the shallot and cook gently for 5 minutes until completely softened. Stir in the garlic and cook for another minute, then add the Jersey Royal potatoes, tomatoes, and chipotle paste with 100ml water. Bring to the boil, cover and simmer gently for 15 minutes until the potatoes are tender. Stir in the beans and cook uncovered for another 5 minutes. Cool slightly.
To serve: spoon the potato mixture into the lettuce leaves, top with avocado slices, a few pickles and a lemon wedge for squeezing over. Garnish with edible flowers and extra lemon wedges.