1. Cook the quail eggs in boiling water for 2 ½ minutes, then drain and cool under running water. Once cooled, gently peel, and then set aside.
2. Mix the shallots in a small bowl with the red wine vinegar and set aside.
3. Cut the potatoes into large even sized pieces. Place in a medium sized pan of salted water and simmer until they are starting to fall apart, around 20 minutes. Drain and leave to dry out for 10 minutes.
4. Put the potatoes through a potato ricer, or simply mash.
5. Mix the potatoes with the flour, egg and melted butter in a medium sized bowl until well combined. Leave to cool completely, and then divide into 4 equal patties.
6. Heat the oil and butter in a large non-stick frying pan and cook the patties on each side for 3 minutes or until golden and crispy.
7. Divide the patties between 2 warm plates, top with the salmon. Cut the quail eggs in half and place on top of the salmon along with the caviar and shallots. Drizzle with rapeseed oil and squeeze over the lemon juice and sprinkle with black pepper.
8. Serve straight away.