Clean and peel all the vegetables. I suggest peeling the red beets last, as they will dye your hands and everything you touch thereafter.

Use a mandoline or a sharp knife and a cutting board to slice everything into thin rounds. If using a knife, take your time and try to make all your cuts as even as possible.

Keep each type of vegetable separate as you slice them, and place into their own bowl. Pour ¼ c. of heavy cream over each vegetable, along with ¼ tsp. of dried thyme, and a good amount of salt and pepper. Toss until each vegetable is coated.

Heat your oven to 400 degrees and grease an oval roasting pan.

Pour the remaining ¼ c. of heavy whipping cream in the bottom of the pan along with the minced garlic.

Grab a stack of sweet potatoes and place the stack cut sides facing up into the pan. Alternate between stacks of beets, parsnips, and sweet potatoes by type until the pan is filled.

Pour any remaining heavy whipping cream from the bowls into the pan. Top with salt and pepper.

Cover with foil and bake for 30 minutes, or until each type of vegetable has softened.

After that, sprinkle with Gruyere and any leftover Parmesan cheese, and bake uncovered for an additional 20 or so minutes.

The dish is ready to serve when the cheese is golden and the vegetables are fork tender.