How to Make It
In a small bowl, mix the wasabi powder with the warm water to make a paste. In a medium bowl, blend the butter with the wasabi paste, sea urchin roe, soy sauce, lemon juice, chives, tarragon, thyme and cayenne. Season with salt and white pepper. Scrape the butter onto a sheet of wax paper and wrap, shaping the butter into a 1-inch-thick log. Let stand at room temperature.
Preheat the broiler. Brush the veal on both sides with 2 teaspoons of the oil and season with salt and pepper. In a large skillet, heat the remaining 1 tablespoon plus 1 teaspoon of oil. Add half the veal medallions to the skillet and pan-fry over high heat until well browned and lightly pink in the center, about 2 minutes per side. Transfer the veal to a rimmed baking sheet and pan-fry the remaining medallions.
Top each veal medallion with 1/2 tablespoon of the wasabi butter and broil 4 inches from the heat for 1 to 2 minutes, basting with the juices and butter and rotating the pan until the meat is golden brown and glazed. Transfer to plates and top each medallion with an additional 1 teaspoon of the wasabi butter. Garnish with the nori strips and serve at once.