Easy Chicken and Corn Chowder

butter

small carrot, finely diced

stalk celery, diced

small onion, finely diced

garlic, minced

all-purpose flour

white corn kernels

yellow corn kernels

russet potatoes, diced

cooked rotisserie chicken breast halves, shredded

chicken stock, divided

half-and-half

nutmeg

salt and ground black pepper