Toss chicken, garlic, ginger, and 1 tablespoon fish sauce in a bowl until the chicken is coated in the marinade. Cover, and marinate for 1 hour.
While the chicken is marinating, heat the peanut oil in a skillet over medium heat. Stir in shallots, garlic, ginger, and chile peppers. Cook and stir until the shallot begins to turn golden brown, about 7 minutes. Reduce heat to low, and stir in peanut butter, coconut milk, soy sauce, brown sugar, 1 1/2 tablespoons fish sauce, and lime juice until blended. Simmer very gently for 10 minutes, then remove from heat and keep warm.
Preheat an outdoor grill for medium-high heat and lightly oil grate. Thread chicken onto skewers.
Grill chicken skewers on preheated grill until no longer pink in the center, about 3 minutes per side. Serve with warm peanut sauce.