Pickled Vegetables: Mix granulated sugar, vinegar and salt in bowl. Add carrots; toss well. Refrigerate at least 1 hour or up to 3 days. Up to 2 hours before serving, stir in peppers and radishes. Refrigerate until ready to use.
For Peanut Sauce: Combine all ingredients with a wire whisk until blended. Store chilled until ready to use.
Chicken Satay: Whisk 1 Tbsp. oil, curry paste, tapioca starch, fish sauce, brown sugar and black pepper in large bowl until smooth. Add chicken and minced lemon grass. Fold in with rubber spatula or mix with electric mixer fitted with paddle attachment 30 seconds or until mixture holds together. Mixture will be sticky.
Place 3 oz. portions on parchment paper-lined half sheet pan. Refrigerate at least 3 hours or until mixture is very firm.
When ready to use, moisten hands and shape each 3 oz. portion into a log about 6-inches long, or as long as the bread for the sandwich. Shape mixture around a lemon grass stalk, leaving leaves exposed. Refrigerate 30 min.
Heat large sauté pan on high heat. Add remaining 2 Tbsp. oil. Sauté skewers on both sides until lightly browned. (Mixture will flatten slightly). Center of meat will NOT be fully cooked. Refrigerate until ready to use. When ready to serve, grill skewers until charred and chicken is done (170°F).
For each serving: Toast 1 roll in 400°F standard oven 3 min. Split lengthwise; spread cut surfaces with 1 oz. sriracha mayonnaise. Place 2 lettuce leaves on bottom half of bread. Remove chicken from lemon grass stalk. Place over lettuce. Drizzle with 1-1/2 oz. Peanut Sauce. Top with 1 oz. Pickled Vegetables, 2 tsp. scallions and 3 sprigs cilantro.