First, preheat the oven to 200 °C convection.
Remove the skin from the shallot and cut into small cubes, cut the anchovy fillets as finely as possible.
Clean the liver, i.e. cut away all tendons, fat and the like. Puree the liver.
Rinse the capers and chop them finely.
Heat a frying pan and melt the butter in it. Sauté the shallots and anchovy fillets in it over medium heat until soft.
Add the wine and stock to the frying pan and cook briefly at a slightly higher temperature.
Reduce the heat once more to medium low, add the liver and capers, stir everything through and cook gently. The liver must be cooked, but should remain creamy. Finally, season with salt, pepper and balsamic vinegar.
At the same time, toast the bread slices in the stove, turning once to the other side. They should be slightly crispy, but not too hard.
Spread the liver farce evenly on top and bring the crostini to the table quickly.