Preheat oven to 400℉.
Saute the onions, carrots, celery, and mushrooms until tender and most of the liquid is cooked off.
Add the saute mixture and the rest of the ingredients into a large bowl and mix very well until incorporated. Add enough rolled oats to create a dry mixture.
Scoop the mixture out into a 4x3 silicone muffin pan.
Bake for 45 minutes or until solid.
