Prepare your veg: trim the very ends off the leeks and halve them. Rinse all the grit out and finely chop them. Peel and finely chop the potato. Warm a large pan for a min. Add 1 tbsp olive oil, the leeks and potato. Season with salt and pepper. Cover. Sweat over a low heat for 10 mins to soften them.
Dissolve the stock cube in 750ml boiling water (or heat up 750ml homemade stock). Peel and crush the garlic. Finely slice the dried figs.
Stir the garlic and half the figs into the pan. Add 1 tsp mixed spice and the thyme sprigs, keeping a sprig back for garnishing. Pour in the vegetable stock. Cover, bring to the boil and then turn the heat down. Simmer for 15 mins till the veg are very soft. Fish out the thyme sprigs.
Ladle the soup into a blender and blitz till smooth, or use a hand-held blender. Add more water if it's a little too thick. Taste and adjust the seasoning if you think it needs more salt and pepper. Ladle into warm bowls. Top with the remaining sliced figs and thyme leaves to serve.