Clean the lamb liver and put it to boil until semi ready. Remove the liver, cut it into thin slices and save the broth. Roll pieces of liver in salt, pepper and flour.
Heat the oil and a bit of butter in a pan and place the thinly sliced onions to fry. Allow to fry for 10-15 minutes, occasionally stirring, then add the crushed cumin and fry for another 5 minutes. Turn the heat up slightly, add the sugar and allow to caramelize, again stirring for 3 minutes.
Then add 2 tablespoons of flour, stir and top up with the wine and broth. Reduce the heat and simmer for 20 minutes. Heat the remaining oil in another pan and fry the pieces of liver for 2-3 minutes on each side.
Drain them on paper towels. Serve a portion of caramelized onion and topped with with lamb liver.