Preheat oven to 400F or 204C.
Bring a large pot of water to boil. Add cauliflower and cook until fork tender.
Heat a large cast iron skillet, add the avocado oil, and add the ground beef. Break it into smaller chunks.
Add onions, celery, and mushrooms to the beef and stir together. Cook for a few minutes.
Then add the mixed veggies and continue to cook, stirring occasionally.
Once the veggies and beef are cooked through, add the garlic, and cook until fragrant.
Add the olive oil, garlic powder, turmeric, salt, and pepper then blend or pulse until smooth like mashed potatoes.
Cover the meat and veggie filling with the mashed cauliflower, then pop it in the oven for 20 minutes, or until it starts to brown on top.
Remove from the oven and serve into bowls. Let cool slightly before eating.