Preheat oven to 220C (425F) and grease a 1L oval pie dish with olive oil
Put cheese into the Thermomix bowl and grate with the measuring cup (MC) on for 6 seconds | Speed 8; remove to a mixing bowl
Put onion and garlic into the Thermomix bowl and chop with the MC on for 3 seconds | Speed 5; add to the bowl with the cheese, season with salt and pepper and stir to combine
Add stock concentrate and 300g of water into the Thermomix bowl and close the lid
Put the sweet potato into the Varoma bowl and tray; keeping some of the holes clear for the steam to get through
Assemble the Varoma on top of the Thermomix and cook for 15 minutes | Varoma | Speed 2
Carefully layer half of the potatoes in the roasting dish and top with half of the cheese, onion and garlic mixture
Slowly pour the liquid in the Thermomix over the potatoes and cheese
Layer the remaining potato and spread the remaining cheese mixture evenly on top
Bake uncovered in the middle shelf of the oven for 25-30 minutes or until the potatoes are cooked through and the cheese is golden brown