Tipsy Lamb 'n' Ginger

• 4 lamb leg bone steaks
• 1 cooking apple (diced)
• 475 gr dry cider
• 150 ml natural yogurt
• 26 gr crystallised ginger (chopped)
• 20 gr tomato puree
• 16 ml oil
• 8 gr demmerara sugar
• 6 ml english mustard
• 2 slices onions (peeled)