Stir the flour and sugar together in a large mixing bowl. Add the cold butter and use a fork to begin to blend the butter into the flour mixture. Then knead it with your hands until the dough comes together in a ball.
Cover the dough with plastic wrap and chill in refrigerator for about 30 minutes.
Preheat oven to 350°F (175°C) and line a baking sheet with baking paper. Divide the dough into four sections and roll each into a long sausage, about as thick as a large index finger.
Use a knife to slice the sausages of dough into small cookies - about 2 in (5 cm). Brush each with whisked egg and decorate with sugar and sliced almonds.
Bake for about 8 - 10 minutes, until golden. Let the cookies cool on a wire rack and enjoy!