Prepare Dough: In a large mixing bowl, pour boiling water over diced butter and lard, whisking together until melted and smooth. Gradually sift in all-purpose flour while mixing until a soft, non-sticky dough forms. Chill the dough in the refrigerator for 45 minutes to 1 hour to firm up.

Make Filling: Heat a skillet over medium heat and add a bit of butter. Sauté diced onions until golden, about 5-7 minutes. Combine onions with diced potatoes, carrots, and cubed stew meat, seasoning the mixture with parsley, thyme, salt, and pepper.

Assemble Pasties: Divide dough into eight equal balls. Roll each into a 9-inch circle. Spoon filling onto one half, dot with butter, moisten edges, fold, and seal by crimping with a fork.

Bake: Preheat to 350°F (175°C) and line a baking sheet with parchment. Place pasties on the sheet, make small slits for steam release. Bake for 30 minutes until lightly golden, brush with cream, and return for another 30 minutes until golden brown.