One of the most useful rules for cooking vegetables is this: if it grows above the ground (stems, leaves!), start it from hot; if it’s grown mostly underground (roots, tubers!), start from cold.
This is especially useful to remember for boiling and simmering: broccoli should go in boiling water, spuds should be brought up to boil. But it also applies to roasted vegetables. Your underground friends could benefit from a slower start – like a parboil, or a cold oven.
That’s because root vegetables are woodier, tougher and hardier. You need to gently heat the outside first to start breaking down the fibres, so by the time the core cooks through the exterior hasn’t disintegrated to mush.
The cold oven start is your secret weapon in this week’s root vegetable tian gratin, AKA rootie tootie cheesy veg bake.
Rootie tootie cheesy root vegetable bake
Starting the bake from cold means your chosen root veg – carrot, parsnip, swede – has the chance to gently soften under the steamy foil ceiling, and is finished with a final blast of direct heat to gratinate (that is, brown) and crisp a little on top.
The word “tian” refers to the spiral arrangement of the veg, as well as the round earthenware dishes these are usually baked in. I like to do mine in a nice big cast iron pan with a handle, and I’m pretty loosey goosey with the veg arranging, too.
I love how this “tian gratin” looks (and sounds!) so fancy, but is actually very straightforward to make – it’s really just about the tessellation and timing.
The creamy cheesy sauce is boosted with the simple addition of a stock cube. I go for “chicken style” ones for quick and convenient flavour.
This is also a handy recipe to have up the sleeve for all the root veg abundant and affordable at the shops right now. And if you get veg box deliveries, they’re probably overflowing with rootie friends at the moment.
If you’re pottering around the kitchen on a weekend, this is the kind of dish that can happily be prepared halfway (up to the step where the vegetables have roasted for one hour), and then finished off the next night for a quicker midweeker. Simply preheat the oven to 180C (160C fan), take off the foil, and continue from the “add the parmesan and gruyere” stage.
You need a pan that can hold a lot of heat, but uncoated cast iron will leave a patina on leftovers (and it isn’t great for the pan either). So consider using a ceramic pie dish if you’re planning on going the “I’ll finish it later” route, and transfer leftovers to a glass container if need be.
Leftovers are delicious the next day as the gratin sets and soaks all the juices up. Simply reheat gently in the oven before eating.
Makes 8 wedgie portions
25g butter
1kg root vegetables such as carrot, parsnip, turnip, swede, radish … get creative!
2-3 waxy potatoes, approximately 400g (sweet potato counts)
1 brown onion, peeled, halved
2 cloves garlic, peeled and finely sliced
5 sprigs thyme, leaves roughly picked, plus extra for garnish
50g parmesan, finely grated
1 “chicken style” stock cube
300ml pouring cream (thickened cream is fine)
Olive oil, to drizzle
100g gruyere cheese, finely grated
For the mesclun salad
100g mesclun, or salad leaves of your choice
1 tbsp lemon juice
3 tbsp extra-virgin olive oil
Grease a 30cm cast-iron pan or ceramic pie dish with the butter and set aside.
Peel root vegetables and potatoes, and place them in a bowl of cold water as you go to prevent them browning. Slice vegetables in half lengthways, then into 5mm-thick half-circles using a food processor with the slice attachment, a mandolin, or patience and a sharp knife. Slice the onion into 5mm-thick half-circles in the same way.
Line the base of the pan with the smaller bobbly end bits of the root vegetables and potatoes to act as a riser, then scatter over half of the garlic and half of the thyme leaves, plus salt and pepper. Starting from the edges of the dish, arrange the sliced root vegetables and potatoes, flat side down, working in a clockwise direction, until the surface of the dish is covered. Arrange the onion and remaining garlic in between the vegetables, distributing them evenly around the pan (you don’t want a giant chunk of onion and garlic in one section!)
Sprinkle over half the parmesan, remaining thyme leaves and more salt and pepper.
Dissolve the stock cube in a tablespoon of just-boiled water. In a medium bowl, combine the stock and cream. Slowly pour the cream mixture over the tian, making sure it gets into all the crevices. Poke in some extra thyme sprigs, drizzle with olive oil and cover tightly with foil.
Place in a cold oven and turn the temperature to 180C (160C fan) and bake for one hour.
Take out of the oven, remove the foil, and check the vegetables are fork-tender (if not, return to the oven until cooked through). Scatter over the gruyere and remaining parmesan and return to the oven for 30 minutes until bubbling and golden on top (you can even turn the grill on high for the last five minutes to really crank the caramelisation).
Carefully remove the tian gratin from the oven (the handles will be hot) and leave to cool for 15 minutes.
In the meantime, to make the mescun salad, soak the mesclun in cold water for 10 minutes then spin dry. In the bottom of your salad bowl, add the lemon juice, glug in the extra virgin olive oil, add salt and pepper to taste, and whisk with a fork to combine.
To serve, toss the leaves around in the dressing to combine. Spoon the pan juices from the bottom of the tian and drizzle over the top of the dish, then slice the tian into eight wedges. Serve immediately with the mesclun salad.
This article was amended on 28 June 2023 to remove suggestions this is a vegetarian dish.
