Pre-heat oven to 375 degrees. Melt the butter in a skillet over medium heat. Add the onions and cook, stirring, for about 10 minutes or until soft and caramelized. Add sage and scrape into a large mixing bowl. Add the cornbread pieces, Chupacabra Rub, and season well with pepper, and give it a good toss to combine well.
In a separate bowl, whisk together the egg, cream, and stock and pour over cornbread mixture. Mix well.
Now spoon into a buttered baking dish, and sprinkle top with a touch more Chupacabra Rub.
Bake until hot and crusty on top, about 30 minutes.