Also - although homemade is always good, there are quite a few natural/organic bottled Ginger/Sesame dressings in the markets these days. In fact, I have yet to try one I didn't really like & that wasn't virtually identical to the one you get in Japanese restaurants. If they're not in the regular salad dressing section, try checking out your market's natural/organic aisle.
This is the real deal - given to me by a Japanese friend -
JAPANESE STEAK HOUSE DRESSING
½ cup oil 1/3 cup catsup 5T onion 3T minced ginger 3T celery 2tsp. lemon juice 3T rice vinegar 2tsp. lemon peel 4tsp. soy sauce ½ tsp. salt ½ tsp. pepper ¼ cup shredded carrot Combine onion, celery, carrot, ginger, lemon peel in food processor and process to a puree; add oil a little at a time as needed; remove from processor, add everything else and mix.