Wash 500g each of potatoes and sweet potatoes (leaving the skins on for extra nutritional benefit), chop into 3cm chunks and cook in a pan of boiling salted water for 15 minutes, or until cooked through. Drain, leave to steam dry and cool, then mash.
Meanwhile, blacken 2 red peppers over a direct flame on the hob or in a griddle pan on a high heat, turning until charred and blistered all over.
Pop into a bowl and cover with clingfilm for 10 minutes, then scrape off most of the black skin, discarding the stalks and seeds. Finely chop, dress with 1 tablespoon of extra virgin olive oil and 2 teaspoons of chipotle Tabasco, then put aside.
Chop 500g of white fish fillets into 1cm dice, then mix into the cool mash really well with a pinch of sea salt and black pepper. Divide the mixture into eight even-sized balls and pat into 3cm-thick patties.
Put two large non-stick frying pans on a medium-low heat with 1 tablespoon of olive oil in each (or cook in batches). Cook four fishcakes in each pan, for 5 minutes on each side, or until golden and cooked through, carefully turning with a fish slice – if they break or crack a little don’t stress, these are light, chunky, rough-and-ready fishcakes.
Meanwhile, peel 1 cucumber, halve lengthways and scrape out the watery core, then slice ½ cm thick. Remove any tatty outer leaves from 1 iceberg lettuce, and roughly chop it into 1cm chunks.
In a bowl, dress both with 1 heaped teaspoon of English mustard, 4 heaped tablespoons of yoghurt and 1 tablespoon of white wine vinegar, mixing well, then taste, season to perfection, and crumble over 40g of feta cheese. Pick, roughly chop and stir through most of the leaves from ½ a bunch of fresh mint (15g).
Serve the fishcakes and salsa scattered with baby mint leaves, with a good portion of salad and wedges of lemon, for squeezing over.