Add the butter and oil to a large pan over a medium heat. When the butter has melted, add in the spring onion tops, thyme, and bay leaves and cook for a minute. Add in the chicken and season well with salt and pepper. Cook for 10 mins, or until the chicken has some light colouring on the outside, then add in the chestnuts. Give the chestnuts a couple of minutes, then stir in the flour. Cook for another couple of minutes, then add in the wine. Combine 3 tablespoons of Bay’s Kitchen concentrated chicken stock with 300ml boiling water and once the wine has bubbled up and reduced, add the stock to the pan.
Continue to stir and cook the filling for another 5-10 minutes and once the chicken has cooked through, add in the lactose-free cream, Dijon mustard, and miso paste. Stir to combine then add in the spinach. Once wilted, take the pan off the heat. Tip the filling into a separate dish or onto a tray and allow it to cool completely.
Heat your oven to 200C, 180C fan, gas mark 6. When cooled, spoon the filling into a medium pie dish with a lip around the edge (I used a dish 29 x 23cm).
Roll out your puff pastry to packet instructions – or large enough to cover your dish with a little leftover. Brush the rim of your pie dish with beaten egg and cut a few strips from the edge of the rolled-out pastry that is wider than the lip of your pie dish. Place your pastry strips on the rim of your pie dish, until it’s completely covered. Brush the pastry rim with egg wash – this gives your pastry lid something to stick to, so now you can place your pastry lid on top, pressing the edges down firmly to ensure they stick. Using a sharp knife, cut off any overhanging pastry from around the edges of the pie, and using your index finger on one hand and the thumb and finger on your other hand, pinch and crimp the pastry all the way around the rim to create a nice fluted edge.
Cut any decorations you like from your leftover pastry scraps and using the beaten egg, stick them to the pastry lid. Brush the top of the pie with egg and using a sharp knife, cut a few small steam holes in the center. Place in the oven and bake for 25-30 minutes, or until the pastry is golden, has puffed up and the filling is piping hot.
To heat the gravy, empty the contents into a clean saucepan and place over a medium-low heat. Slowly bring to the boil and once piping hot, tip into a jug to serve with the pie.