Preheat oven to 350 degrees. Grease an 8 x 8 inch pan with lard or avocado oil.

Bring a pot of water to a boil. Peel and chop Japanese yams. Add yams with a 1/2 tsp of salt. Boil until tender (8-10 minutes). Mash and set aside.

Chop onions, celery, and bacon. Heat lard or avocado oil on medium heat. Add onions, celery, and bacon to the pan. Cook until golden brown and beginning to crisp up.

Puree onions, celery, and bacon in blender or food processor until mostly smooth. Add pureed mixture to mashed yams along with the chicken broth, nutritional yeast, sage, and salt. Stir all ingredients together and spoon into greased pan.

If desired, add some shredded AIP Parmesan cheese for some extra cheesy flavor.

Bake in the oven for 30 minutes until lightly golden brown. Let cool for 5 minutes before serving.