Guinness lamb shank

INGREDIENTS

• 3 red onions, peeled
• olive oil
• sea salt
• ground pepper
• 2 handfuls raisins
• 3 heaped tablespoons thick-cut marmalade
• 1 heaped tablespoon tomato ketchup
• 2 tablespoons Worcestershire sauce, plus extra for serving
• 200 ml Guinness or smooth dark ale
• 6 quality lamb shanks, roughly 350g each
• 8 sprigs fresh rosemary
• 1 litre organic chicken stock
• 1 small bunch fresh mint leaves
• a few tablespoons rapeseed or olive oil
• 2 spring onions, trimmed
• cider vinegar