In a small mixing bowl, combine the olive oil, mustard, lemon juice, hot sauce, and garlic. Season with salt and pepper. Whisk to blend well. Season the prawns with salt and pepper. Place 2 prawns on each skewer and place in a large resealable plastic bag. Pour half of the dressing over the prawns, seal the bag and shake several times to evenly distribute the dressing over each prawn. Place in the refrigerator and allow to marinate for 1 hour. Remove from the bag and bring to room temperature. Preheat the grill. Place skewers on the grill and cook for 2 to 3 minutes on each side, or until the prawns turn bright pink and their tails curl in. In a medium mixing bowl, combine the corn, basil, onion, tomatoes, and bell pepper. Add the remaining dressing and toss to mix. Cover and chill for at least 2 hours before serving. Using 3 to 6 spears of asparagus, form a triangle in the center of each serving plate. Spoon the corn and tomato mixture in the center of each plate. Lay 2 to 3 skewers on top of the salad. Garnish with green onions