#1 In a small saucepan, combine the soy sauce, mirin, sake, rice vinegar, sugar, grated ginger, and grated garlic. Heat over low heat and stir until the sugar is dissolved. Remove from heat and let the sauce thicken and cool to room temperature #2 Season the tuna steaks with salt and pepper. In a non-stick skillet, heat the vegetable oil over high heat. When the pan is very hot, add the tuna steaks and sear for about 30 seconds to 1 minute on each side. You want to sear the edges as well for a short time. The goal is to sear the outside while keeping the center rare to medium-rare. If using a grill pan, you can create grill marks by rotating the tuna during searing. Remove the tuna from the pan and let it rest for a few minutes #3 Using a very sharp knife, slice the seared tuna into thin, even slices. The slices should be about 1/4 inch thick #4 Arrange the sliced tuna on a bed of microgreens or arugula on a serving platter. Drizzle the tataki sauce over the tuna. Garnish with chopped green onions, sesame seeds, and, if desired, a sprinkle of red pepper flakes for some heat. Serve immediately and enjoy!