Preheat oven to 230°c and place a rack in the top third of the oven
Place 500g of the potatoes on a baking tray lined with baking paper and toss together with 1tbsp of oil and ½ tsp salt flakes. Bake for 20-25 minutes, tossing halfway through, until golden brown and cooked through. Set aside to cool, then very roughly crush them.Meanwhile, place the remaining 250g potatoes in a medium saucepan over medium high heat. Cover with cold, well-salted water and bring to a simmer. Cook for 12 mins or until soft. Drain and set aside to cool.
Place olive oil in a small saucepan over medium-high heat. Add the 12 picked Thai basil leaves and the wakame and fry for 1 minute, stirring a little until crispy. Strain, reserving the oil and transfer the aromatics to a small plate lined with paper towel.
Roughly crush the boiled potatoes (some lumps are fine) and add to a large bowl with the roasted potatoes, ginger, long green shallot, garlic, lime zest, potato flour, egg, chopped basil and ⅛ tsp of salt flakes (or a little more, depending on how salty your potatoes are). Finely chop half of the crispy wakame and add to the bowl. Mix everything together well, then add the salmon and gently mix to combine, trying not to break the salmon pieces too much.
With lightly oiled hands, form the mixture into 8 fishcakes weighing about 110g each, compressing them as you go so they hold together.
Place half the butter and 1tbsp of reserved oil in a large frypan over high heat. Lower the heat to medium and fry half the fish cakes for 2-3 mins until crisp and golden. Fry the remaining fish cakes the same way using the remainder of the butter and oil.
Plate up and serve with ginger & thai basil yoghurt sprinkled with the crispy wakame and leaves.
Place all ingredients in a bowl and mix to combine with a good pinch of salt. Set aside until ready to use.