Peel the potatoes, cut them into 5cm wide chunks and place them in a high pot covered in water. Add 1 tsp of salt and put on medium to medium high heat. Put a colander over the pot.
When the potatoes start cooking, place the salmon filets into the colander and cover it with aluminum foil, so the steam won't escape. Steam the salmon for 5-8 minutes. Take out and set aside.
Cook the potatoes until they are soft, around 20-25 minutes. Drain and mash them while still hot. Set aside to cool for 10-15 minutes.
Meanwhile make the dip by mixing yoghurt, garlic, parsley and zest and juice of one lemon together. Season with salt and pepper. Set aside.
Add the juice and zest of two lemons, the parsley, the egg, the flour and salt and pepper to taste to the potatoes. Gently break the steamed salmon into chunks and add as well. Mix everything.
Heat a large frying pan with 3 tbsp of olive oil over medium high heat.
Form the fishcakes and carefully dust them with flour. Fry them in batches until they are golden brown and crispy on each side.