Julienne green lettuce leaves and put in a shallow bowl. Sprinkle all-purpose flour and mix to coat. Set aside.
In a bowl, combine ground beef, minced onion, grated ginger, salt, soy sauce, sesame oil and corn starch. Mix well. Take about 2 tablespoons of mixture and form into balls. Put one ball into the julienne lettuce bowl, coat julienne lettuce and press a ball into shape. Repeat this one by one.
Circle half of balls up on a large microwave safe plate. Put the plate in a microwave, cover with plastic wrap and cook on high in the microwave for 6-8 minutes or until all balls are cooked through. Repeat this with the rest of balls. (if your microwave is big enough to cook all balls at one time, you don't need to cook them in twice. Circle all balls up on the plate and cook!)
Serve with Ponzu or soy sauce and yellow mustard sauce.