1. Put the unpeeled mandarins in a saucepan, add water to cover them, bring to the boil and cook for 45 minutes. (If using oranges cook for an hour)

2. Preheat oven to 190C fan-forced (200C regular) and grease a large loaf tin with butter. 

3. Cream the butter, sugar and vanilla seeds with an electric mixer until pale. Add the eggs one at a time, beating after each addition.

4. Add the flour, a quarter at a time, still beating. Put the dates in the water and bring to the boil in a large saucepan. Add the bicarb soda - the mixture will rise and froth. Pour the dates and liquid into the creamed butter and eggs and mix. 

5. Cut the mandarins into rough chunks and fold through the batter.

6. Pour the batter into the tin, up to about two centimetres from the top. Put the loaf tin in a deep tray and fill the tray with water to halfway up the loaf tin. Cover the deep tray in foil and bake in the oven for 55 minutes or until a skewer comes out clean. When the pudding is ready, slice it into thick pieces, put in serving bowls, pour over butterscotch sauce and serve with double cream or ice cream.

For butterscotch sauce

Put the sugar into a very clean saucepan over a medium heat. Don't stir it. When the sugar melts and turns a dark caramel colour, add the butter and cream while stirring – the mixture will boil intensely at first. Once it subsides, remove the pan from the heat immediately. If there are crystallised sugar lumps in the sauce, pass it through a fine strainer. If not, pour the sauce into a container ready to serve. Don't refrigerate, as it will solidify.