Prepare the Filling:
Coat the Meat:
In a bowl, toss the beef and kidney pieces with flour, salt, and pepper until evenly coated.
Brown the Meat:
Heat 2 tablespoons oil or butter in a large pot over medium-high heat.
Sear the beef and kidneys in batches until browned on all sides. Remove from the pot and set aside.
Cook the Vegetables:
In the same pot, add onions and garlic. Cook for 3-4 minutes until softened.
Make the Gravy:
Stir in tomato paste, then pour in the beef stock, ale (if using), Worcestershire sauce, thyme, and bay leaf.
Return the browned beef and kidneys to the pot.
Bring to a simmer, cover, and cook on low heat for 1 ½ hours, stirring occasionally.
Thicken the Gravy (Optional):
If the sauce is too thin, stir in cornstarch mixed with water and simmer until thickened.
Remove from heat and let the filling cool while preparing the pastry.
Prepare the Pastry:
Make the Dough:
In a bowl, mix flour and salt. Add cold butter and rub it into the flour with your fingertips until it resembles breadcrumbs.
Gradually add cold water, stirring until the dough comes together.
Wrap in plastic wrap and chill for 30 minutes.
Preheat the Oven:
Set oven to 375°F (190°C).
Assemble the Pie:
Roll Out the Pastry:
On a floured surface, roll out ⅔ of the dough and press it into a 9-inch pie dish or individual ramekins.
Fill with the cooled steak and kidney mixture.
Top and Seal:
Roll out the remaining pastry and place it over the filling. Trim the edges and crimp to seal.
Brush the top with beaten egg and cut a small slit in the center for steam to escape.
Bake:
Bake for 30-35 minutes, until golden brown.
Serve:
Let the pie rest for 5 minutes, then slice and serve warm.