This is how I make my soup.
Add 200ml-250ml water to a ball-whisk shaker, add the soup powder, black pepper, and whatever else you are using to spice it. Shake until all mixed up, pour into a container and microwave for 2-3 minutes. Pour into a bowl and eat
I found using just water from the kettle didn't make it hot enough for long enough, and using a stick blender made the soup too frothy.