For the liver
Place a frying pan over high heat and add sunflower oil. Season the liver with salt and flour on all sides. Place in the frying pan and fry on all sides until golden brown. Remove onto absorbent paper, place on a baking dish lined with parchment paper and cook in a preheated oven at 160°C to taste, making sure however that it doesn’t dry out.
For the balsamic vinegar sauce
Place a frying pan over high heat, add the butter and cook until it turns a light golden brown colour and releases an intense aroma. Add the vinegar (be careful, it will bubble), stock and raisins. Cook for a further 2 minutes, then add onion and balsamic syrup. Season and add herbs.