Procedure Chicken: In a large bowl, combine the chicken, garlic, cumin, oil, salt and pepper. Toss well and set aside. Sauce: Using a sharp vegetable peeler, take the zest off the oranges and cut it into julienne strips. In a medium saucepan bring 2 cups of water to a boil and add the strips; cook about 30 seconds, strain, and rinse with cold water. Juice the oranges (you should have about 2 cups of juice). Wipe out the saucepan and add the orange juice and strips, the vinegar, the brown sugar, and the chile powder. Bring to a boil over medium heat; reduce to simmer and cook until reduced by half, about 15 minutes. Just before serving, add the cilantro. This can be made ahead and refrigerated until needed. Preheat a barbeque grill or a grill pan. When hot, add the chicken thighs and cook until cooked through and lightly charred, about 4 minutes per side. Remove from heat; let rest for about 5 minutes. Put a chicken thigh on each plate and top with a tablespoon of warm sauce.