Gather your mise en place; get together all of the equipment needed for the recipe and gather your ingredients.

Cut the onion in half and remove the peel, then slice thinly with the grain. 

In a medium frying pan, add the butter and melt over medium heat. Add the sliced onion and cook until softened and slightly browned. Add the white wine, smoked paprika, thyme, sage, nutmeg and bring to a boil. Once the wine has reduced by half in volume, add the cream and return to a simmer. Once simmered, remove from the heat and set aside. 

Peel the parsnips, sweet potatoes, beets and carrots. Using a mandolin, thinly slice all of the root vegetables. 

Preheat the oven to 425°F. 

Grease a sheet pan lined with parchment with butter, or alternatively a casserole dish. 

Arrange the thinly sliced vegetables across the sheet pan slightly overlapping. Sprinkle grated parmesan cheese and salt and pepper on top. 

Use a ladle to pour the warm cream mixture over the vegetables evenly. 

Cover the sheet pan with another layer of parchment and tightly wrap in tinfoil. 

Bake until the vegetables have softened, roughly 20 to 25 minutes. Once the vegetables are just fork tender, remove the tinfoil and top layer of parchment and sprinkle the grated gruyere all over top. 

Return to the oven and bake for another 10 – 15 minutes, until the gruyere has melted and begun to brown slightly. 

Finish with more black pepper and serve immediately.