Serve these leeks later in the day, or, even, better, the following day.
2. Combine the onion, olive oil, and carrots in a large, heavy casserole and cook over medium heat, stirring, for 2 to 3 minutes. Stir in the leeks and sugar, cover with a sheet of crumpled parchment paper or foil and a tight-fitting lid, reduce the heat to low, and cook for 20 minutes. (Leeks and carrots should cook in their own moisture. If necessary, add 1 tablespoon water.)
3. Meanwhile, in a small bowl, soak the rice in hot water to cover for 10 minutes; drain.
4. Add the rice to the leeks. Season with salt and pepper, and cook, tightly covered, over low heat for 20 minutes longer.
5. Remove from the heat and add the lemon juice. Leave the pan uncovered to cool before transferring the leeks to a serving dish. Spoon the vegetables and rice over the leeks, garnish with the chopped parsley, and serve at room temperature or chilled.
Adam Rapoport, editor in chief of Bon Appetit magazine and the website www.bonappetit.com, knows his way around a grill. He has edited an entire book on the subject: The Grilling Book: The Definitive Guide from Bon Appetit.