Preheat your oven to 400°F and grease a 3-quart casserole dish with butter.
Boil water in a saucepan, then blanch broccoli florets for about 2 minutes, and drain them immediately.
In a skillet, melt the butter over medium heat, and add the chicken breasts to cook until browned thoroughly on both sides.
Transfer the cooked chicken to the casserole dish, arranging the broccoli on top.
Pour the chicken broth over them.
In a bowl, mix the cream, cheese, and sage, then pour this mixture over the chicken and broccoli.
Bake for 25-30 minutes.