Roll the dough out thinly on a lightly floured surface or using a pasta machine. Using a round, or square, biscuit cutter, stamp out rounds of pasta. Pipe or spoon your chosen filling into the middle of each round. Brush the edges with beaten egg and carefully fold the round into a crescent shape, excluding all air. Bend the two corners round to meet each other and press well to seal. Repeat with the remaining dough. Leave to dry on a floured tea towel for about 30 minutes before cooking.