Warm up the milk on the stove or microwave, then stir in the butter and salt. Slowly add in the flour and combine until proper consistency, making sure not to allow it to clump.
Allow to stand for 15 minutes, followed by a cool-down in the refrigerator for about a half-hour.
Meanwhile, in a large bowl, it's time to make the filling. Mix the chopped meat, mutton fat, and diced onions, and throw in a pinch or two of the various spices, to taste.
Take the prepared dough, roll it out until very thin (about 3-5 mm). Depending on how you want to shape the samsas, cut some squares (usually about 5 cm²).
Put a scoop of the meat and mutton fat filling in the center of each square, and then fold it over and pinch the sides shut, as a standard dumpling.
Placing them on a standard baking sheet (greased), crack the egg and brush onto the top of each samsa. A common tradition has it to sprinkle some sesame seeds on top.
Place in oven and bake until golden brown on top, 205°C (400°F) for about 20 minutes, followed by flipping them over and another 15 minutes or so at a reduced 175°C (350°F).