In a bowl, add cubed tofu and marinade ingredients: soy sauce, cornstarch, baking soda, water and oil. Allow to marinate while you prepare other ingredients.
In a small bowl, mix together sauce ingredients: light soy sauce, dark soy sauce, sesame oil and sugar. Leave to side.
Prepare veggies - slice bok choy and onions.
Prepare rice noodles by separating or cut if in a large sheet to 1-inch wide. If noodles are stuck together, blanch for 30 seconds in boiling water and drain, leave to side.
Heat up pan with oil to medium heat. Add onions and bok choy to cook until softened, add garlic. Remove from heat and add more oil to cook tofu.
Add veggies back into pan with noodles and sauce. Stir fry and lift up noodles to mix well!