Heat 2 tablespoons butter over low heat. When melted, stir in tamari and Yuzu juice. Set aside.
Heat 1 tablespoon of butter in a large skillet over medium heat. Trim and add chestnut mushrooms, and sauté for 5 to 10 minutes, or until browned and tender. Season with salt and keep warm.
Pat sea scallops dry, removing the tough muscle on the side. Place wasabi powder on a small plate, and dip the flat sides of each scallop in the wasabi powder. Place scallops on a plate.
Heat the remaining tablespoon of butter in a small skillet over medium-high heat. When butter is bubbling, add the sea scallops. Cook over medium-high heat for one minute, then reduce heat to medium. (Over higher heat, the wasabi powder tends to burn.) Continue cooking until the first side is golden brown, then turn and cook the other side until golden brown.
Rewarm the tamari Butter and whisk well to emulsify. Divide the tamari butter between two serving plates. Place cooked scallops on the sauce, top with sautéed mushrooms, and then with zested curls from the lemon. Serve immediately.