• 1 tbsp olive oil, plus extra for greasing
• 1 onion, finely chopped
• 2 x 110g packs baby leeks, chopped
• 800g pork sausages, skinned
• 2 tbsp chopped sage leaves
• small bunch flat-leaf parsley, chopped
• 4 rashers smoked streaky bacon, chopped
• 1 tbsp wholegrain mustard
• 40g mature Cheddar, grated
• 2 x 375g packs ready-rolled puff pastry