From: https://profoodhomemade.com/chicken-ham-and-mushroom-pies/
Making the hot water crust pastry:
Mix the salt and flour together
Place the water on a low heat, add the butter and lard to the pan, bring to a simmer.
Soon as the fats have melted, pour the hot liquid onto the flour in the bowl, and bring it all together.
Tip the contents of the bowl out onto a non floured surface.
Gently knead the dough until it all comes together.
Cut the pastry onto 2 equal pieces.
Cover in plastic wrap or food bags, and place in the fridge for at least 1 hour before using.
Making the Pie Filling:
Melt the butter in a medium size saucepan, on a low to medium heat.
Add your diced chicken pieces, stir-fry until they turn white and firm up.
Add the salt, black and white pepper, and dried thyme, mix those in.
Add the garlic, followed by the mushrooms, and mix those in.
Stir in the flour and the vinegar, and thoroughly mix.