Toast each nori sheet by holding one corner and moving sheet back and forth over a medium-hot electric burner or low gas flame just until nori turns green. Do not over-toast. Using scissors, cut into 4- or 5-inch squares. Stack on a plate or place in a serving basket.
Combine rice and 1/3 cup of the seasoned rice vinegar in a bowl. Mix well and set aside.
Bring remaining 1/3 cup seasoned rice vinegar to a boil in a small saucepan. Add carrots. Cook and stir until tender-crisp. Drain and set aside
Steam spinach or mustard greens until Just limp. Drain and set aside
Slice avocado into small, thin sections. Moisten all sides with lemon Juice to prevent discoloration. Set aside.
In a small skillet, saute tofu strips with scallions in vegetable oil until tofu is lightly browned.
Arrange tofu, carrots, spinach or mustard greens, avocado, mushrooms, cucumber and pickled ginger slices on a tray. Divide the rice between two serving bowls and place alongside tray on your serving table. Add a small bowl of goma-miso furikake seasoning and a bowl of tamari.
Stir together Sesame Sauce ingredients and serve in a bowl. Place nori sheets on the table.
To roll sushi: Hold a piece of nori flat in the palm of your hand. Spoon a small amount of seasoned rice into the center. Top with your choice of foods from the sushi tray. (Don't pile too high!) Spoon a little seasoning, Sesame Sauce and/ or tamari over filling. Overlap corners to enclose filling.
Note: Check at an oriental grocery for the specialty items listed. Nori sheets are sometimes available pre-toasted and can be used right from the package.