Brush a 1 1/2 litre capacity ovenproof dish with 20g butter.
Place the sour cream, consommé, onion, garlic, thyme, nutmeg, salt & pepper together in a small saucepan over medium heat.
Bring to the boil, cook for 2 minutes & remove from the heat. Cover surface with plastic wrap & leave to stand for 15 minutes.
For the topping, place the breadcrumbs, remaining butter, parsley & parmesan together in a bowl & mix until well combined. Set aside.
Bring a large saucepan of water to the boil, blanch the root vegetable slices in batches for 2 minutes each & refresh in cold water. Make sure you keep each root vegetable separate.
Place a layer of the blanched root vegetables followed by a tablespoon full of the cream mixture. Repeat the process until all the root vegetable slices have been used.
Pour over remaining cream mixture & sprinkle with the breadcrumb topping.
Bake in preheated oven for 1 hour, or until the gratin is bubbling & golden.
Three ways with root vegetables:
For a hearty soup, cook 1 chopped onion, 1 red chilli, 1 teaspoon each of ground cumin
& coriander with 1 tablespoon olive oil in a large saucepan until soft. Add 1kg peeled chopped mixed root vegetables (eg. sweet potato, carrots & parsnip), 1/3 cup dried red lentils & 1 1/4 litres vegetable stock. Bring to boil & cook for 30 minutes or until vegetables are tender & lentils are soft. Add a handful of coriander leaves, puree with a stick blender until smooth & season with salt & pepper.
For roast veggies, toss 2kg peeled & chopped mixed root vegetables (eg. parsnips, carrots, beetroot, sweet potato & celeriac) with 1/3 cup mixed herbs (lemon thyme, rosemary, sage), 4 cloves garlic, salt & pepper, until well coated. Divide between 2 baking trays and roast at 200°C for 45 minutes or until tender & golden.
For a mash with a difference steam or boil 1kg of mixed root vegetables (eg. potato, celeriac, parsnips & swede) until tender. Drain well, then mash until smooth.
Add 40g butter, 1/4 cup milk & season well with salt & pepper, stirring until well combined.