Vary the vegetables and grains in this recipe if you like.  You could use cauliflower florets or courgettes for instance and French salad dressing makes an alternative and quick marinade. Rice or quinoa make good alternatives to buckwheat.

1. Preheat the oven to 200°C (180°C fan) Gas mark 6 and add the sweet potatoes wrapped in foil.
2. Make the marinade by whisking together the marinade ingredients in a large pan or bowl.  Then put two tablespoons of the mixture to one side to use later.
3. Toss the vegetables in the marinade and lay on a large baking tray with a small gap between each piece (add the asparagus halfway through cooking to prevent it becoming too soft).
4. Roast for 20-30 minutes or until all the vegetable are just cooked, checking halfway through cooking and removing any that are browning too quickly to the middle of the tray.
5. Meanwhile, cook the buckwheat in lots of boiling water for about 10 minutes, or until tender, but be careful not to over cook as it quickly turns to mush.  Drain in a sieve.
6. Once the sweet potatoes are soft to touch, remove them from the oven and scoop out the centre of each potato into a bowl.  Add the remaining marinade and tahini and mash until smooth and creamy.  Add a little hot water if necessary to produce a very soft mixture and season with salt and pepper.
7. Serve the mash on the buckwheat and pile the roast vegetables on top.