For dipping sauce, in a small saucepan stir together the coconut milk and cornstarch. Cook and stir, uncovered, over low heat for 3 to 5 minutes. Set mixture aside to cool. Meanwhile, in a small mixing bowl combine the wasabi paste, the grated ginger, and 1/2 to 1 teaspoon of the lime juice. Stir in thickened coconut milk mixture and cool, covered, in refrigerator.
Peel and devein shrimp, leaving tails on, if desired. In a large skillet or wok heat oil on medium-high heat for 30 seconds. Cook shrimp 2 minutes, turning once. Add soy sauce, garlic, and, if desired, pepper. Cook for 30 seconds to 1 minute more or until shrimp are opaque.
Remove skillet or wok from heat. Sprinkle remaining lime juice over shrimp mixture. Serve with dipping sauce. Makes 4 side-dish servings.