1. Melt the butter in a frying pan with half a tablespoon of olive oil. Add the shallots, and fry gently till golden brown but not crisp.
2. Toss in the sprouts and stir fry with the shallots until just softened.
3. Mix in a bowl with the mashed potato.
4. Season with salt, pepper and nutmeg. Allow to cool.
5. Divide the mixture into four patties using plain flour on your hands to help shape the mixture.
6. Fry the patties in olive oil and a little butter until golden brown on both sides. This takes 5-6 minutes.