In a cast iron skillet, heat medium-high and add finely chopped onion. Sauté until translucent, then add shredded beef and a splash of Guinness stout. Stir in thyme and a pinch of salt, simmer uncovered for about 30 minutes.

In a mixing bowl, combine cold butter and flour until it resembles coarse crumbs. Gradually add salt and mix until just combined. Chill pastry dough for at least 20 minutes.

Roll out the chilled pastry to 1/8-inch thickness. Use a round cutter to create circles and place spoonfuls of beef filling in the center. Fold over, press edges to seal and crimp with a fork.

Preheat the oven to 350°F (175°C). Whisk egg with a splash of water for wash and brush over the tops of each hand pie.

Bake on a parchment-lined baking sheet for 18-22 minutes until golden brown. Rotate halfway through.

Cool the hand pies on a wire rack for a few minutes before serving warm.