Cook brussels sprouts briefly in boiling water for no more than 3 minutes, just long enough to thaw the sprouts. Do not let them become soft. The vegetables should be crisp when marinated.
Drain thoroughly so that water doesn't dilute the marinade.
Put remaining ingredients in a bowl and mix with a wire whisk.
Combine marinade with brussels sprouts. Refrigerate vegetable mixture in a plastic or glass covered container overnight.