Add it at the beginning of making the stock with the leftover vegetables - we put everything in ours.

Then make soup from the stock and leftover vegetables.

For example, roast leftover vegetables for ten minutes and then add macaroni cheese on top.

Then take all your leftover vegetables (roast potatoes, sprouts, parsnips, etc), add cooked pumpkin or chestnuts if you fancy, and break it up a little using a fork.

Any leftover vegetables - even in a casserole - are liquidised for soup.