In a saucepan over medium high heat, heat water to boiling. Add udon noodles. Cook until noodles are softened, 4 to 5 minutes.

Add rotisserie chicken. Turn heat to low. Remove 2 to 3 tablespoons water, and stir miso paste into water until smooth. Mix diluted miso paste back into noodles. Cook for 2 to 3 minutes.

Ladle soup into bowls and garnish with everything bagel seasoning.