01 -
Warm your oven to 200°C. Rub the soft butter all over your 3-quart baking dish.
02 -
Grab a mandoline to cut your sweet potatoes, parsnips, and beets into super thin circles. Put each veggie in its own bowl.
03 -
Add 4 tbsp cream to both sweet potatoes and parsnips, and just 2 tbsp for the beets. Sprinkle ½ ounce Parmesan and 1 tsp thyme into each bowl. Add plenty of salt and pepper, then mix everything till all slices are coated.
04 -
Pour what's left of the cream (60ml) into the buttered dish. Scatter ½ ounce Parmesan and all the chopped garlic on top.
05 -
Stand the veggie slices upright in rows, going sweet potato, parsnip, then beet. Keep this pattern going until you've got about 6 rows filled with all your veggies.
06 -
Sprinkle some salt, pepper, and whatever Parmesan you've got left over the top.
07 -
Cover with foil and pop in the oven for 30 minutes until the veggies start getting soft.
08 -
Take off the foil and sprinkle the Gruyère all over the top of your dish.
09 -
Put it back in the oven without any covering for another 18-20 minutes. You'll know it's done when you can easily stick a fork in the veggies, the cheese has melted, and the top looks slightly brown.
10 -
Throw some fresh thyme leaves on top before you bring it to the table.