Chestnut & cranberry roll

INGREDIENTS

• 1 tbsp olive oil
• 1 onion , finely chopped
• 2 Bramley apples , approx 140/5oz each, peeled
• 3 x 450g/1lb packs good-quality pork sausage
• 2 x 200g/7oz packs vacuum-packed chestnuts , roughly chopped
• small bunch parsley , leaves roughly chopped
• small bunch sage , leaves roughly chopped
• small bunch thyme , leaves stripped
• 1 egg
• 100g white breadcrumbs
• 175g fresh or frozen cranberries
• 24 rashers streaky bacon
• butter , for greasing