Preheat the oven to broil. Place the chicken, onion, celery, carrot, and garlic in a roasting pan. Coat lightly with vegetable oil and broil until lightly browned. Remove and add enough water to cover the chicken and vegetables. Add jalapeño and tomato and place the roasting pan over medium high heat. Bring to a boil, then cover and simmer 30 - 45 minutes. Cool the chicken in the broth. Remove skin and bone the chicken.

Sauté the garlic and onion in a small amount of vegetable oil over medium heat. Set aside. Using two forks, shred the meat and toss it with the onion mixture. Season with salt and pepper and moisten with some of the cooking broth.