Cook the frozen peas and spring onion in the boiling water with the stock concentrate or stock cube until tender and cooked through.

Remove and discard the spring onion once the peas are soft enough to be blitzed into soup.

Chop up the mozzarella roughly and put it in the blender - or a processor, but soup is always more velvety when liquidizes in a blender - with the peas and their liquid. I do this in about 3 batches, pouring the soup back into the pan and heating it gently to meld the cheese and peas better together. Otherwise just set aside and reheat later.