For the Sauce:
4 tablespoons butter
1/2 cup all-purpose flour
2 cups chicken broth
1 jar (16 ounces) salsa verde (2 cups)
1 can (5 ounces) evaporated milk (or 2/3 cup half and half)
18 oz (about 4.5 cups) cooked, chopped chicken

For the cornbread:
1 cup milk
3 tablespoons butter
1 1/2 cups all-purpose flour
1/2 cup yellow cornmeal
1 tablespoon baking powder
1 teaspoon salt
1/4 – 1/2 cup thinly sliced scallion greens