Preheat a griddle pan or frying pan on a medium-high heat. Mix together the mustard, brown sugar, oil, salt and pepper in a small bowl. Spread the mixture on the chicken breasts.
Place the chicken breasts on the griddle and cook for 3-5 minutes on each side until cooked through, and no longer pink in the middle. Remove from the heat and place on a chopping board to rest.
Cook the noodles as per the pack instructions, then drain and rinse with cold water to prevent the noodles from sticking together.
Use a mandoline to julienne the red cabbage, carrot, radishes, red pepper, yellow pepper and green cabbage (or finely slice if you don’t have a mandoline). Finely slice the spring onions into 3cm long strips.
Mix together all of the dressing ingredients in a small bowl.
Assemble the bowls by adding in the vegetables and noodles, then tossing together. Slice the cooked chicken and arrange on top of the bowls. Drizzle on the dressing and serve.