Brown sausage until it's golden brown. As you are cooking it, continue stirring, breaking the meat into tiny pieces. Remove it from the skillet and place it into a large bowl, set aside.
Dice mushrooms into small pieces. Place them with butter into the same skillet where you cooked sausage and cook until they turn golden brown. Add in diced green onions.
Place the mushroom mixture into the sausage, add in bread crumbs and stir to combine everything together.
Place the mixture into a baking dish. Pour chicken stock over the mixture. Bake at 350F for 45 minutes.
Remove from the oven and serve it while it's still warm.