1) Peel and trim the asparagus stalks. Cut about 2 1/2cm of the tips from the spears and then thinly slice the remaining stalk. Bring a small saucepan of salted water to the boil. Drop the asparagus into the water and cook until just crisp yet tender, about 1 minute. Drain and refresh under cold running water. Set aside.
2) In a medium bowl, whisk together the garlic, shallot, mustard, lemon zest and juice, salt and pepper to taste. Gradually whisk in the oil to make a creamy dressing.
3) In a large bowl, combine the rice, nuts, carrots, celery, asparagus, dill and mint. Toss with about 85ml of the dressing. Serve as is or toss the lettuce with some of the dressing.
To serve, place the lettuce on a serving platter or individual plates and spoon the salad into the centre of the leaves. Pass any remaining dressing at the table.