Wash the potatoes, put them in a small pot and cover with water. Bring to the boil, reduce the heat, and simmer until the potatoes are soft, about 15 minutes or so. Meanwhile, prepare the yogurt dressing. In a small bowl, combine the yogurt, garlic, lemon juice and season with salt a pepper. Stir in about half of the dill.
Strain the potatoes and let them sit for a while to cool down. Arrange potatoes and salmon on plates, sprinkle with the remaining dill and spring onion. Finally, spoon over the yogurt dressing and serve.