Place the lamb in a large bowl and mix with the mint, coriander, oregano, garlic, sherry, vinegar and molasses. Season with cumin, allspice, chilli flakes, salt and black pepper then mix well. Shape into 4 patties.
Brush BBQ grate with oil. Cook burgers 5 minutes on each side or until well done.
Heat the pita pocket briefly on the BBQ. Serve burgers wrapped in pitas with feta cheese.