1. Steam or boil the potatoes for 10-15 minutes, or until just tender (pierce with the point of a small sharp knife—if the potato comes away easily, it is ready). Drain well.
   
   
   
   
2. Put the milk in a large pan and heat up. Add the cooked potato and half the butter, then mash well with a potato masher until smooth and creamy.
   
   
   
   
3. Melt half the remaining butter in a large heavy-based ovenproof pan and cook the selection of green vegetables until they are tender. Add to the mashed potato, mix together and season well with salt and freshly ground black pepper.
   
   
   
   
4. Preheat a grill. Melt the remaining butter in the same pan, then spoon in the potato mixture, smoothing off the top. Cook until the bottom is golden brown and crispy. Remove from the heat and place under the grill until the top is also crisp and golden. If you prefer, you can turn the potato mixture over in the pan and cook on the other side, but grilling is easier.
   
   
   
   
5. Fill a deep heavy-based pan a third full of oil and heat to 180°C (350°F) (a cube of bread dropped in the oil will brown in 15 seconds). Cook the croquettes in batches for 5 minutes, or until golden. Remove carefully with a slotted spoon, drain on paper towels and keep warm while cooking the remaining croquettes.

Variation: This is also delicious with some chopped bacon cooked with the greens.