Step by step recipe:

1. 25 min.
   Prepare and chop 1 leek.
   
   Prepare and chop 1 shallot.
2. 5 min.
   Cut 250 g salmon fillet into 2 cm (1 inch) cubes, or thereabouts, keeping only the flesh and removing any skin and bones.
3. 2 min.
   Pour 2 tablespoons olive oil into a non-stick pan on medium heat. When this is hot, add the chopped shallot, salt and pepper and cook for 1 or 2 minutes.
4. 7 min.
   Then add the chopped leek and mix well. Cook uncovered until the leek is just tender but still nice and green.
   
   Remove from the heat and keep hot.
5. 4 min.
   Pour 2 tablespoons olive oil into a frying pan and once this is nice and hot add the cubes of salmon. Cook for a bare 2 to 3 minutes, so that the cubes are browned on the sides. Do not cook any longer or you will end up with salmon purée.
   
   Remove the salmon from the pan onto a plate and set aside.
6. 3 min.
   Put the pan back on medium heat and add 100 g feta cut into small pieces. Stir until it is melted.
7. 5 min.
   Add 150 g plain yoghurt and 1 teaspoon tomato paste, and bring to the boil while stirring.
   
   Heat the serving plates.
8. 5 min.
   Return the salmon cubes to the pan and stir gently. Add the juice of ½ lemon if you like and remove from the heat.
9. 5 min.
   Arrange on the plates: lay a bed of leek and pour the salmon and sauce on top.
   
   Serve without delay.