Roll out the pastry into a rectangle measuring 40 × 30cm/16 × 12in. Cut into 10cm/4in squares. On each square, make a 2.5cm/1in diagonal cut from each corner towards the centre. Mix the ground almonds, icing sugar and egg together. Divide the filling among the pastry squares, placing it in the centre.
Beat the egg yolk for the glaze with half the wate