Meanwhile, remove the ends of the asparagus spears and cut them in half.
Place them in the boiling water to cook for 2 minutes.
Remove the spears from the water and set them to the side.
Toast the sourdough bread and butter it. (Depending on the size of the slices, you may not need all of the butter.)
Using a sharp knife, halve the avocado, then with a spoon, scoop out each half of the flesh and slice it thinly.
Begin to assemble the avocado toast by placing half of the asparagus spears onto each slice of buttered sourdough, and topping each with half of the sliced avocado.
To poach the eggs, heat water in a small saucepan until it is bubbling very lightly, then add the white wine vinegar.
Crack an egg into a small bowl.
Using a spoon, stir the hot water for 10 seconds to create a small whirlpool, then gently slide the egg from the bowl into the center.
Cook the egg for 3 minutes until the white is set, then remove it from the water using a slotted spoon.
Place it on a kitchen towel and cut off any stringy parts, then repeat the process with the second egg.
Place the poached eggs over the avocado and top each with half of the chives and sumac, then season with salt and pepper.
Place half of the rocket on the side of each plate, then serve immediately.