Soften the diced onions and garlic in a little water on a medium heat in a large saucepan. Add diced potato and broccoli florets to the pan and cover for 5 minutes. Crumble the stock cube into the 1.2L of water then pour into the pan and simmer for 20 minutes until the broccoli and potato are tender.
Blend the soup mixture using a food processor or blender until smooth. Return the soup to the heat and add 75g of crumbled cheese and stir to melt. Ladle into warmed bowls and serve with lumps of remaining cheese on top.