Preheat oven to 400. Place the chicken, sage, salt and pepper in a pan and cover it with the broth. You need to make sure the chicken is covered with the broth. If not add more chicken broth or add water. Bring the chicken to a simmer, cover and cook 30-45 mins or until done.
Shred the cooked chicken. Mix the cream of chicken, 1 cup of chicken broth from cooking the chicken, hashbrowns, cheese, 1/2 cup of the french onions, frozen veggies, melted butter, and sour cream together in a large bowl until mixed. Pour into a greased 9x13 baking dish and top with french onions. Bake in the oven.