Slice the chicken breast into long 1/2 inch wide strips. To make a marinade, drop the garlic cloves and jalapeno peppers through the feed tube of a food processor with the chopping blade in place and the motor running until chopped finely (10 seconds or so).
Add the remaining ingredients and process until smooth (about another 10 seconds). Pour the marinade over the chicken and let marinate for 2 hours at room temperature or overnight in the refrigerator, turning occasionally.
Preheat the oven broiler. Drain the chicken, reserving the marinade. Arrange the chicken on a rack on a broiler tray and broil 3 inches from the heat source for 5 minutes; turn, baste with marinade, and broil for another five minutes.
Serve with warmed tortillas, shredded lettuce, shredded cheese, chopped tomatoes and salsa verde.
1 1/2 lb Boneless chicken breast
1/3 c Dry Sherry
2 x Garlic cloves
1 tb Chili Powder
2 x Jalapeno peppers
2 ts Ground cumin
1/2 c Olive Oil