To cook noodles, add to a pot of boiling water for 1½ minutes, stirring occasionally. Drain, rinse with cold water, then drain again, until dry. Add 2 tablespoons of canola oil to a heavy skillet with medium heat. Add the well-drained noodles, slightly flattening into a round pile. Cook both sides until crispy, approximately 5 to 6 minutes. Blot off excess oil with a paper towel. Transfer to serving plates.
To make sauce, sauté garlic and ginger with 2 tablespoons canola and 3 teaspoons sesame oil. Add oyster sauce. Thicken with corn starch slurry (using water). Salt and pepper to taste.
For the fish, preheat oven to 350 F. Season Mahi-mahi with salt and pepper. In a large skillet using medium high heat, add canola oil. Pan sear Mahi-mahi fillets on both sides for 1½ minutes each. Put the skillet with the fillets in the oven for another 2½ minutes until firm to touch (medium well done). Place the Mahi-mahi on top of the noodles with vegetables, pour the hot oyster sauce around the edge of the noodles on each plate and serve immediately.