Heat your oven to 200°C/Fan 180°C/Gas 6. Slice the squash in half and scoop out the seeds. Slice it into wedges around 2cm wide. Tip them into a roasting tin. Add 1 tbsp oil, a pinch of chilli flakes, ½ tsp cinnamon and some salt and pepper.
Drizzle in the tamarind. Turn the wedges a few times so they are well coated. Roast for 30 mins till the squash is tender and a little charred.
While the squash roasts, peel and finely slice the shallots. Peel and crush the garlic. Crumble the stock cube into a heatproof jug. Stir in 350ml boiling water.
Warm ½ tbsp oil in a pan. Add the shallots. Season with a good pinch of salt and pepper. Fry over a medium heat, stirring often, for 5 mins till soft and golden. Stir in the garlic.
Stir in the pearl barley. Add the bay leaf and thyme sprigs. Pour in the vegetable stock. Cover and bring to the boil. Turn down the heat and simmer for 15 mins till the stock is absorbed and the barley is tender.
While the barley cooks, tip the peanuts into a dry frying pan. Toast over a medium heat for 2-3 mins, shaking the pan often, till golden. Tip out onto a board. Let them cool for a few mins, then rub off any skins and roughly chop them.
Lift the thyme sprigs and bay leaf out of the barley. Taste the barley and add more salt and pepper if you think it needs it. Spoon the barley pilaf into wide, shallow bowls. Scatter over handfuls of lamb’s lettuce.
Top the barley with spoonfuls of the Greek yogurt, the roast squash wedges and chopped peanuts. Add a final pinch of chilli flakes to garnish.