To make the sweet potato and coconut cream
Peel the sweet potato and put aside a few very thin slices for decoration, dice the rest.
Open the can of coconut milk, pour into a non-stick pan with chopped lemon grass. Add the diced sweet potato and bring to the boil. Turn down the heat and simmer until tender (approx. 20 minutes).
Purée finely, then season with salt and harissa.
To make the roasted vegetables
Heat oven to 200°C/400°F/gas mark 6.
Peel and dice sweet potatoes. Toss with oil in a baking dish. Sprinkle over some coarse salt. Cover and bake for half an hour, then remove cover and allow to crisp up for 10-20 minutes.
Do the same as above with the turnips (no need to peel). Sprinkle over some fresh thyme leaves before serving.
Place the leek in a thin layer of foil with olive oil, salt and pepper, wrap it, then bake in oven for 10 minutes.
Place the sweet potato cream on a plate and arrange roasted vegetables and garnish on top.
Garnish with sliced sweet potatoes, turtle beans, tendril pea shoots and finish with pumpkin oil.