To make Confit Spice: Combine all ingredients and store in an airtight container. (Yield: about 2 cups)
To make Soy-Lemon Dressing: In a bowl, whisk ingredients to combine. Refrigerate until needed. If making ahead, reserve herbs until the last minute, as they will darken.(Yield: 2 2/3 cups)
Trim tuna of any skin, blood line and excess connective tissue. Coat with Confit Spice. Heat a heavy-bottomed pan until medium-hot. Place oil in the bottom. Working very quickly, sear each side of the spiced tuna for 20 seconds. This will set the spice and remove any raw taste from it. Cool quickly and refrigerate.
Slice tuna very thin and arrange on a plate with fanned avocado, daikon sprouts, pickled ginger, enoki mushrooms, black sesame seeds and triangles of toasted nori. Spoon approximately 2 tablespoons Soy-Lemon Dressing on the plate.
Adapted from Chef Gary Danko, Restaurant Gary Danko, San Francisco, CA