Ingredients

30g unsalted butter

700g large white onions, peeled, halved and sliced

Salt

1 tablespoon of olive oil

200g button mushrooms, stalks trimmed and halved

150ml turkey stock

500g leftover turkey, diced

200g tin rustic bean mix or white beans (drained weight) rinsed

4 tablespoons coarsely chopped flat leaf parsley plus extra to serve (optional)

For the top

200g wholemeal breadcrumbs

75g turkey gravy or stock

3 tablespoons extra virgin olive oil

Method

• Melt the butter in a large saucepan over a low heat.  Add the onions, sprinkle over a teaspoon of salt and gently fry over a low heat for 30 minutes, stirring frequently to prevent them colouring.  By the end they should be silky and soft.

• Meanwhile, heat the oil in a large nonstick frying pan over a medium high heat, then fry the mushrooms for several minutes until lightly coloured, stirring occasionally and transfer to a medium bowl.

• Puree the onions with the stock in a blender until silky smooth then transfer the sauce to a large bowl and leave to cool for about 30 minutes.  Stir in the turkey, mushrooms, beans and parsley.

• Transfer this to a shallow ovenproof dish (around 20cm x 30cm).  The filling can be prepared well in advance, in which case cover and chill.

• To cook the pie, preheat the oven to 200C/190Cfan/gas 6 ½ . For the top whiz the breadcrumbs with the gravy and oil to a crumble consistency in a food processor taking care not to turn it into a dough.  Scatter over the filling and bake for 20-35 minutes until the crumbs are golden.