Step 1
Cut flour lard cold butter and 1 1/2 teaspoons salt together in a bowl with a pastry blender until mixture has the consistency of coarse crumbs. Make a well in the center and pour in ice water. Mix with a fork until mixture begins to come together; use hands to form into a dough ball.
Step 2
Turn dough out onto a lightly-floured work surface and knead until dough is smooth and forms a firm ball about 2 minutes. Wrap dough tightly in plastic wrap and refrigerate until chilled at least 2 hours.
Step 3
Preheat oven to 350 degrees F (175 degrees C). Line a baking sheet with a silicone baking mat.
Step 4
Stir steak potatoes onion turnip 1 1/2 teaspoons salt black pepper and cayenne pepper together in a bowl until evenly-combined.
Step 5
Beat egg and 1 teaspoon water together in a small bowl.
Step 6
Divide dough into 4 equal rounds and roll each round out to about 1/8-inch thickness and 8-inches in diameter. Brush each dough round with egg mixture.
Step 7
Place 1/4 of the steak mixture slightly off-center on each round of dough and top steak mixture with 2 slices butter. Fold dough over steak filling to form a half moon shape and press edges together to seal. Trim excess dough from edges of pasties. Transfer pasties to the prepared baking sheet and crimp edges with the tines of a fork; poke fork 1 time into the top center of each pasty and brush tops with egg mixture.
Step 8
Bake in the preheated oven until browned and bubbly about 1 hour. Cool on a wire rack for 5 to 10 minutes.