Grease Slow Cooker:

Grease the slow cooker insert with butter or nonstick spray.

Chop Vegetables:

Chop the celery and/or onion into small cubes.

Sauté Vegetables:

In a skillet over medium heat, melt the butter and cook the diced vegetables until they start to become tender.

Combine Ingredients:

Combine all components thoroughly.

Slow Cook Mixture:

Transfer the mixture to the slow cooker. Put the lid on and set to low for 4 to 5 hours.

Transfer to Oven Dish:

For oven method: Complete steps 1 through 4 as in the slow cooker instructions, then place the mixture into a buttered or oiled 9x13-inch oven-safe dish. Cover with foil.

Bake Covered Then Uncovered:

Bake at 350°F (preheated) for 25 minutes. Then remove the foil and continue baking for another 15 to 20 minutes until the edges turn crispy.

Freeze Mixture:

For freezer method: Finish steps 1 through 4 as per the slow cooker method, then place the mixture into a labeled gallon-size freezer bag. Store in the freezer for up to 6 weeks.

Thaw and Cook:

To cook from frozen: Thaw the bag overnight in the fridge. Select your preferred cooking method from above, transfer the mixture to the correct pan or insert, and cook following that method's directions. Refer to Notes.