Open out the pastry, and using a bowl or plate as a guide cut out four 16cm circles. You will need to re-roll the pastry to get all 4 circles. Place around 3 tablespoons of filling on the right hand side of each of the pastry circles, then fold over the empty half, and lightly push the edges together to form a seal. To create the classic pasty crimp pattern, start at the top of the semicircle, make a small 1-2 cm forwards fold over the seal, then repeat the folds all the way around the semicircle edge of the pasty. Place all of the pasties on a baking tray and use a pastry brush to wash all over with egg yolk.