Place frozen udon noodles in a microwave-safe dish, cover loosely with plastic wrap, and heat according to package instructions until softened.

Cut the salmon into bite-sized pieces and season both sides with salt and pepper.

Cut the arugula into bite-sized pieces and slice the onion thinly.

Heat butter in a frying pan over medium heat, add salmon, onion, and half of the arugula, and sauté until the onion becomes tender.

Add the seasoning ingredients (milk, cream, grated cheese, salt, soy sauce, consomme, and pepper) to the pan and bring to a boil.