Heat a pot of water.In a heatproof bowl(I prefer borosilicate or steal) add the yogurt.
Place the bowl with yogurt on top of the simmering water(the bottom not touching the water)
Keep whisking the yogurt and you will see it thicken and warm up slightly.Keep doing this for about 5 minutes and then remove from the heat.Add Salt.
Use the same pot of boiling water-reduce the heat so that the water is simmering and not boiling.
Break an egg in a ramekin or a small bowl.Sprinkle the vinegar on top of the egg as Nigela says-aiming for the white.
Tip the egg gently in the water and do not disturb for 2 minutes.The egg should come up automatically but if it doesn't nudge it with a spatula.At about 3-4 minutes the egg will be cooked but the yolk will still be runny.
Using a slotted spoon take the poached egg out.Place it on the yogurt.
Heat the butter in a small pan.Once it starts to bubble add the paprika,sumac and the garlic clove.Switch off the gas before the paprika starts to burn.
Tip this tempering over the yogurt and egg and enjoy!