Chop the cabbage and red ginger.
Heat vegetable oil in a frying pan and lightly cook the cabbage and red ginger. Add in the yakisoba noodles and cook while following the package instructions.
In a separate bowl, mix the egg and dashi. Mix well.
For this step, you will be using a rectangular pan (Rolled Egg Omelet pan). Heat oil in the pan and pour in 1/3 of the egg mixture from Step 3. Spread the mixture to thin layer and place the yakisoba noodles from Step 2. Starting from the edge, roll the egg towards you. Once you roll the egg with yakisoba, pour in another 1/3 of the mixture to the space and thinly spread to a layer. Roll up from the edge and repeat the procedure. Once you are done with the mixture, shape the egg omelet using a spatula. Atsuyaki Tamago, a.k.a. Rolled Egg Omelet is ready!
Mix Japanese mayonnaise with country mustard and spread on bread (One side only).
Sandwich the the rolled egg omelet from Step 3 with the breads from Step 5. Slice off the crust if necessary and cut the sandwich to 3 slices. Place the sandwich on a plate and garnish with mini tomatoes. Enjoy!