Striped Bass Grilled in Banana Leaves

INGREDIENTS

• 6 large garlic cloves, halved
• 1 piece fresh ginger, 1 inch long, peeled
• 3 Tbs. fresh cilantro roots or stems
• 3/4 tsp. salt
• 3/4 tsp. whole peppercorns, cracked
• 1 1/2 Tbs. Chinese light soy sauce
• 2 whole striped bass, sea bass, red snapper or trout, each about 1 1/2 lb., heads and tails intact
• Salt and freshly ground pepper, to taste
• 2 stalks lemongrass, trimmed, crushed and cut into 2-inch lengths
• 2 large banana leaves, or more if needed
• 1 Tbs. vegetable oil, or as needed
• 4 green serrano chilies, chopped
• 3 garlic cloves, chopped
• 1 shallot, chopped
• 1/3 cup chicken broth
• 1 Tbs. sugar
• 1/4 tsp. salt
• Juice of 2 limes
• 2 Tbs. chopped fresh cilantro