Pull the leaves and silks from the sweetcorn cobs. Slice a sliver off the bases of the cobs, so they stand upright on your chopping board, then run your knife down the cobs to remove the kernels.
Place a large pan on the hob for 2 mins. When warm, add in the corn kernels. Toast them for 3-4 mins on a medium heat, stirring them every now and then till most of the kernels are a light golden brown. Transfer the toasted corn to a bowl and set aside.
While the corn toasts, peel and finely chop the onion. Halve the pepper and scoop out the seeds and while pith. Finely chop the pepper to match the onion. Once you've scooped the corn out of the pan, add 1 tbsp olive oil, the onion and pepper. Cook on a low heat, stirring, for 8 mins till starting to soften.
While the onion and pepper cook, peel and finely chop the garlic. Halve the chilli and finely chop it, removing the seeds and white pith for less heat. Peel and chop the potato into 1cm-thick chunks.
When the pepper and onion has softened add the cumin seeds, garlic, chilli and potato with a good pinch of salt and pepper. Fry together for 2 mins. Add the corn back to the pan and stir. Pour in the milk and 200ml cold water. Bring up to a bubble, then simmer on a low heat for 15 mins, till the potato is soft.
While the soup is cooking, trim and thinly slice the spring onion. Finely chop the parsley stalks. Roughly chop the leaves keeping them separate from the leaves.
When the potato is soft, stir the parsley stalks into the pan. Taste the soup and season with salt and pepper. Ladle half the soup into a blender and blitz till smooth or use a hand-held blender in the pan, pulsing it a few times to half-blend the soup (or lave i chunky if you prefer).
Ladle to soup into a couple of bowls. Crumble 50g feta over each. Sprinkle over the parsley leaves, crack over a little black pepper and serve.