Melt the butter in a medium to large saucepan, and add the potatoes and onion, salt and pepper. Cover with a piece of wax paper and sweat over a gentle heat for 10 minutes. Meanwhile, cut the broccoli florets from the stalk. Using a small knife, remove the outer layer of skin from the stalk and discard, then chop the stalk into 1/2-inch pieces. Add to the onion and potato, cover and sweat for a further 5 minutes.  Add the hot stock to the potatoes, onion and broccoli stalk, bring up to a boil, then add the chopped broccoli florets. Boil without the lid over a high heat for 4–5 minutes until soft, then add the cream. Remove from the heat, puree in a blender and season to taste.To make the Dubliner toasts, toast the bread on both sides, sprinkle with grated Dubliner Cheese and pop under a hot grill or into a hot oven for 2 minutes or until the cheese melts. Cut the toast into fingers and serve on the side with the soup.