Do ahead: The fajitas filling can be made up to two hours ahead and reheated in a sauté pan just before serving. If making ahead, don’t cook it right to the end of the suggested cooking time, as it might dry out when reheated. Tortillas may be softened and held, wrapped in a damp towel, in a warm oven for up to 30 minutes.
1. Combine chicken, garlic, chili powder and 3 tablespoons olive oil in a bowl. Stir to mix evenly, wrap tightly and store in the refrigerator for at least 1 hour and up to overnight.
2. Take 1 jalapeño and cut off the stem. Cut the pepper in half, remove the seeds and membrane and finely chop the flesh. Stem the second jalapeño and cut it crosswise into very thin slices. Set aside.
3. In a large sauté pan, heat 3 tablespoons olive oil. Add onion and sauté over moderately high heat, stirring occasionally, until onion starts to brown, about 10 minutes. Add red pepper, green pepper and finely chopped jalapeño. Sauté, stirring occasionally until peppers are wilted, about 7 minutes. Add chicken, and continue cooking until chicken is opaque and cooked through, about 5 minutes. Keep an eye on the mixture as you may need to add a little more oil. Remove pan from heat and stir in water or tequila, cilantro, salt and pepper.
4. To prepare tortillas, heat a dry sauté pan over moderate heat. Set flour tortillas in pan one at a time to soften. Heat for 10 seconds, then flip and repeat on the other side. Transfer warm tortillas to a large square of foil and package and hold in a 200° oven for up to 30 minutes.
5. Arrange a platter of warm tortillas and bowls of sour cream, salsa, grated cheddar, sliced jalapeño and lime wedges. Serve chicken with onions and peppers in a large bowl. Invite your guests to assemble their own fajitas.
For the Fresh Tomato Salsa:
In a medium bowl, combine tomatoes, onions, scallions, cilantro, jalapeño, garlic, lime juice, olive oil and salt. Mix thoroughly. If desired, add hot sauce to taste.
Beef Fajitas: Substitute 1 ½ pounds beef for the chicken.