Preheat oven to 400 F, spray a 9 x 13 baking dish with pan spray

In a medium bowl, toss 1 cup of cheese with the xanthan gum, making sure the xanthan gum is well distributed. Set aside.

In a medium or large saucepan, saute onions in butter until they soften, about 5 minutes. Add garlic, continue to cook for 1 more minute.

Add heavy cream and chicken stock, whisking well to combine.

As mixture starts to boil, add the shredded cheese and xanthan gum mixture, continue stirring until melted and smooth. Remove from heat, season with salt and pepper to taste.

Slice turnips VERY thinly. I like to use a mandolin, as it saves time.

Layer about a third of the turnips in the prepared casserole dish. Pour a third of the sauce over it, tilting the pan to let it seep through the layers.

Layer another third of the turnip slices, pouring another third of the sauce over it. Repeat one more time, using up the remaining turnips and sauce. Cover with foil.

Bake for 1 hour. Remove foil, return to oven for another 20 minutes.

Serve hot!