1. For the Lemon Grass and Lychee Coulis, microwave coconut milk in small microwavable bowl on HIGH 20 to 30 seconds. Add lemongrass pieces; let stand 10 minutes. Place coconut milk, lemongrass, lychee, lime juice, ginger and Kecap Manis in blender container; cover. Blend 30 seconds or until lemongrass is shredded. Strain mixture, pressing solids with spoon to extract liquid. Set aside.
2. Prepare ice water bath in large bowl; set aside. Trim root ends of bok choy. Separate into leaves and rinse. Bring large saucepot of salted water to boil. Add boy choy; cook 30 seconds. Drain. Transfer to ice water to stop cooking process. Place bok choy on paper towels. Set aside.
3. Mix panko and sesame seeds on large plate. Cut tuna into 4 steaks. Moisten lightly with water. Season tuna with 1/2 teaspoon of the sea salt. Coat on both sides with sesame seed mixture, pressing firmly so the mixture adheres to the tuna. Heat 2 tablespoons of the oil in large skillet on medium-high heat. For medium-rare tuna, cook 1 to 1 1/2 minutes on each side. Remove tuna to plate; cover loosely with foil to keep warm.
4. Heat remaining 1 tablespoon oil in same large skillet on medium-high heat. Add bok choy and lychee; cook and stir 1 minute or just until heated through. Season to taste with remaining 1/2 teaspoon salt and pepper grinder. To serve, slice tuna into thin slices. Arrange bok choy mixture in center of each plate. Top with tuna slices. Drizzle with Lemon Grass and Lychee Coulis.
Test Kitchen Tip: Kecap Manis is a thick sweet soy sauce, typically used in Indonesian cooking. It can be found in Asian groceries.