Peel and finely chop the onion. Trim and chop the carrot (no need to peel). Peel and crush the garlic. Peel, quarter and core the apples. Cut them into small chunks.
Heat a pan over a medium heat for 1 min. Add ½ tbsp oil. Add the prepped veg, garlic and apples. Season with a pinch of salt and pepper. Gently fry for 5 mins, stirring occasionally.
Add ½ tsp mixed spice and stir to coat the veg. Crumble in the stock cube and pour in 1 ltr boiling water. Simmer for 10 mins.
Finely shred the spring greens, discarding any really thick bits of core. Set a small handful to one side.
After the soup has simmered for 10 mins, add most of the spring greens. Stir and cook for 2 mins to wilt them. Blend the soup till smooth with a hand-held blender, or ladle into a blender and blitz till smooth.
Add the reserved shredded spring greens to the soup and finely grate in the zest from the lemon. Add the juice from half the lemon. Taste and adjust the seasoning, adding more lemon juice if you think it needs it. Ladle into warm bowls to serve.