First, put some oil in your large frying pan. Turn the heat to a medium level. Put the sausages into the hot pan carefully. Cook them until the outsides look brown and crispy. You do not need to cook them fully yet. Take them out and put them on a plate.

Keep the fat in the same frying pan. Add the chopped red onions to the warm fat. Stir them around for about five minutes. They should become very soft and look clear. This builds a sweet base for your pie.

Sprinkle the plain flour over the soft onions. Stir it in well for one minute. This cooks the raw taste out of the flour. It will look like a thick paste in the pan.

Slowly pour the beef stock into the frying pan. Stir the mix constantly while you pour the liquid. This stops lumps from forming in your gravy. Let the sauce simmer and get thick and glossy.

Now, add the Worcestershire sauce and the dried thyme. Put a little salt and pepper in the mix. Cut the sausages into large chunks and add them. Stir everything so the sausages are covered in sauce.

Pour the sausage mix into your deep pie dish. Spread the meat out so it is very even. Let the mix cool down for a few minutes. This keeps the pastry from getting too soft.

Dust your table with a little bit of flour. Roll the puff pastry out with your rolling pin. Make sure the pastry is larger than your dish. It should be about the thickness of a coin.

Place the pastry over the top of the dish. Press the edges down with a fork to seal. Brush the top with the whisked egg wash. Put the pie in a hot oven for forty minutes. Bake until the top is high and golden brown.