In a very large saucepan, add 15g of butter and all of the vegetables except the tomatoes and beetroot. Gently saute until everything is soft - this will take about 5-10 minutes.
Add the boiling water, seasoning (salt and pepper), tomatoes and beetroot and simmer to boil until everything is tender. This should take about 10-15 minutes.
Season more to taste if needed, stir in the remaining 15g of butter and fresh mint and enjoy!