1. Blanch the spinach for a couple of minutes in a large saucepan of boiling water. Drain thoroughly, pressing out as much liquid as possible with the back of a wooden spoon.

2. Heat 2 tablespoons of the olive oil in a large frying pan over medium heat. Add the garlic and spinach and cook gently until the garlic is transparent. Season to taste and remove the pan from the heat.

3. Heat the remaining oil in another frying pan large enough to take the liver in a single layer. Add the liver and fry for 3 minutes over medium-high heat. Turn the slices over, add the butter and cook for another 2 minutes. Remove the liver from the pan and keep warm.

4. Add the drained sultanas, pine nuts and balsamic vinegar to the pan in which you cooked the liver. Stir over medium heat until reduced. Season to taste.

5. Meanwhile, reheat the spinach and transfer to a warmed serving dish.

6. Place the liver on top of the spinach, pour over the reduced sauce and serve immediately.