Heat oil in large pan over high heat until almost smoking. Add mushrooms and cook until golden brown. Add garlic and cook 1 minute. Divide mizuna and mushrooms among 4 plates. Drizzle with the White Truffle Vinaigrette and sprinkle with sage.
Place shallots, vinegar and mustard in a blender and blend until smooth. With the motor running add olive oil and blend until emulsified. Add truffle oil, salt and pepper and blend for 2 seconds more.