Heat a cast iron skillet over medium heat. Add the beef and brown it for 5–7 minutes. Add the finely chopped onions and thyme, cooking for 3–4 minutes until the onions soften.

Pour in the Guinness and allow the filling to simmer for 10–12 minutes, stirring occasionally until it thickens. Remove from heat and let it cool completely.

In a mixing bowl, combine flour and salt, then cut in cold butter until resembling coarse crumbs. Gradually add cold water until the dough comes together. Form into a ball, wrap in plastic, and refrigerate for at least 30 minutes.

Preheat your oven to 350°F (175°C). Roll out the chilled pastry dough to 1/8-inch thickness. Cut out circles and place a tablespoon of filling on half of the circles. Moisten edges with egg wash, fold, and seal.

Place on a lined baking sheet, brush the tops with egg wash, and bake for 18–22 minutes until golden brown, rotating halfway through.

Cool slightly on a wire rack and serve warm with mustard or a salad.