Wash the liver well and remove the membranes. Cut it into pieces. Heat the butter and fry the chopped onion, garlic and mushrooms. Once tender, add the liver with spices and sugar to them. Fry for a few minutes while stirring and pour in the cream. Stir and when it starts to thicken, remove it from the heat.
Put everything into a blender or food processor. Deglaze the pan with the wine and brandy and allow to simmer until the liquid is reduced by half. Add it to the liver with the softened butter but set aside about 1-2 tablespoons of butter.
Blend the entire mixture well and then pour it into fireproof containers. Put zest on top and pour on the melted butter to seal. Put it to bake in a water bath in a moderate oven for about 10-15 minutes.
Refrigerate the ready pâté. You can skip the final baking process, if the pork liver is cooked well enough during frying.