Step 1

Place the butter in a large skillet and melt over medium heat. Add the celery, onion, salt and pepper and cook for 4 minutes. Add the mushrooms and garlic and cook for another 4 minutes, stirring occasionally. Remove the vegetables from the heat.

Step 2

Meanwhile, in the base of a 6-quart slow-cooker, whisk to combine the mushroom soup, chicken broth, egg, parsley, rosemary and sage. Add the bread and fold all together into the cubes are well coated. Gently fold in the vegetable mixture.

Step 3

Cover and cook on high heat for 30 minutes. Then reduce the heat to low for 2 more hours. The top of the stuffing should be steaming and the temperature in the center should be around 160 degrees when finished cooking. Transfer to a serving bowl, or hold on warm heat in the slow-cooker, covered, for up to 1 hour.