Pat the tuna steaks dry with paper towels to remove excess moisture. Mix salt, ginger, and white pepper together in a small bowl. Coat both sides of the fish with the mixture, and rub about one tablespoon of the cornstarch on the sides of the steaks. Cover and refrigerate for 30 minutes. Mix the green chilies with the remaining tablespoons of the cornstarch, water, and sugar in a small saucepan over medium heat. Add the peanut oil, minced garlic, and chicken broth, and blend well. Bring to a boil and stir constantly, until thickened a bit. Cool and reserve for basting while grilling the tuna steaks. To prepare the green onions, cut them into thin, vertical, string-like slices and reserve for a garnish. Prepare the grill for moderate cooking. Brush the grates of the grill with oil to prevent sticking. Grill the tuna steaks about 4 or 5 minutes on each side, making sure to baste frequently with the prepared liquid. Grilling time will vary with the thickness of the steaks; estimate 10 minutes per inch of thickness. Line a serving platter with spinach or lettuce leaves, and place the fish on the bed of greens, garnishing with the green onion strings. Posted to dailyrecipe@recipe-a-day.com by Recipe-a-Day on May 16, 1999, converted by MM_Buster v2.0l.