Peel and chop the onion into thick slices. Peel and crush the garlic. Peel the sweet potato and cut it into 2 cm cubes. Cut the lamb into 1 cm pieces.
Heat ½ tbsp oil in a large pan over a medium heat. Fry the lamb for 3-4 mins till browned on all sides. Remove to a plate with a slotted spoon.
Add the onion to the pan with ½ tbsp oil if needed. Fry for 2 mins. Turn the heat down. Add the garlic and 1 tsp each of the cinnamon and cumin seeds. Cook for 1 min till the pan smells fragrant. Tip the lamb back into the pan. Stir to coat it in the spices.
Crumble the stock cube into a measuring jug and dissolve with 1 ltr boiling water. Pour the stock into the pan. Season. Cover and gently simmer for 20 mins. Zest and juice half the lemon. Cut the other half into wedges.
Rinse the rice and add to the pan. Stir, cover and simmer for 5 mins. Drain and rinse the chickpeas, then add to the pan. Add in the sweet potato and the lemon juice. Cover and simmer for 15 mins. Top up with a little more water if needed.
While the harira is simmering, heat your grill to its highest setting. Cut the figs in half, through the stalk. Place on a tray and grill for 2 mins till softened and beginning to caramelise. Chop four of the fig halves into small pieces.
Stir the chopped figs through the lamb harira. Chop the mint leaves and stir half into the pan. Taste and adjust the seasoning if it needs it.
Ladle the harira into bowls. Top each with half a grilled fig. Scatter with the remaining mint leaves and the lemon zest. Serve with lemon wedges.