Preheat the oven to 350 degrees F.
In a skillet, brown the ground beef.
Add the potatoes and cauliflower to a large saucepan filled with water and boil until soft.
Drain the potatoes and add to a casserole dish
Top potatoes with minced onion.
Spoon browned ground beef over top of the potatoes.
In the saucepan used for the potatoes, add butter and melt over medium low heat.
Once melted, add arrowroot powder and mix well.
Cook butter mixture for about 5 minutes to allow it to thickened.
Add the milk or heavy cream and mix well.
Add the cheese a bit at a time, stir and allow it to melt fully.
Pour mixture over potato and ground beef mixture.
Place casserole dish into the oven.
Cook for 30 minutes.