In a jar with a tight fitting lid, combine the garlic, ginger, soy sauce, rice vinegar, peanut oil, sesame oil and hot pepper sauce. Close the lid and shake vigorously to blend. Set aside to let the flavours blend.
Bring a large pot of water to a boil. Add udon noodles and cook until tender, about 3 minutes. Drain and place in a serving bowl.
In a microwave-safe bowl, combine the green, red and yellow capsicums with spring onion and peas. Heat in the microwave until warm but still crisp. Add to the noodles in the bowl and pour the dressing over all. Toss to coat everything in dressing, then sprinkle toasted sesame seeds over the top.
Toast sesame seeds in a dry frypan over medium heat. Shake pan, or stir occasionally until lightly browned, about 3 minutes.