Cut each of the flattened veal cutlets into 4 on-the-spot strips and the liver into about 16 on-the-spot pieces. Season with salt, pepper and sage.
Roll each piece of liver into a cutlet strip. Slide 4 rolls each onto a metal skewer, alternating with tomato slices. Heat fat in frying pan. Brush the meat with it.
Place the skewers on the grill and grill for 5-10 minutes per side. Repeatedly brush with fat in between.
Salt, season with pepper and bring to the table on the spot.