In a large skillet, heat oil over medium high heat. Add celery and onion, season with salt and pepper, and sauté for about 5 minutes or until they begin to soften. Add mushrooms and garlic and continue to sauté until mushrooms are cooked.
Remove from heat, add butter and let the butter melt, stirring as needed. Stir in herbs, black pepper and chicken broth.
In a large bowl, beat the two eggs. Add cubed stuffing and pour the vegetables and broth over the stuffing. Stir to combine and put into a 7-quart slow cooker that has been sprayed with nonstick cooking spray.
Cook on High for 1 hour, and then reduce heat and cook on Low for 4 to 6 hours. If your dinner isn't ready yet, set your crockpot to Warm.
Vegetarian: Simply substitute vegetable stock for the chicken stock.
Meat-lovers: If desired, omit the mushrooms. Brown sausage or bacon to add to the stuffing. I love to add cooked and chopped turkey giblets and neck meat, too. Remove them from the cavity of the turkey and simmer in a small saucepan until they're tender. Chop finely.
More Add-Ins: Try chopped apple, dried cranberries, raisins, or chestnuts.
Storage Tips: Put stuffing into a covered container. Leftover stuffing will keep three to four days in the refrigerator or up to three months in the freezer.