<p>Preheat the oven to 180C</p>
<p>1. Cut a pocket in each of the chicken breasts and fill with a generous sprinkling of grated parmigiano reggiano, and then add about a dozen rocket leaves.</p>
<p>2. Wrap the breasts in one or two pieces of prosciutto.</p>
<p>3. Cut the puff pastry into four pieces and roll out each into a rectangle that is large enough to wrap the chicken breast.&nbsp; Brush the edges of the pieces of pastry with beaten egg.</p>
<p>4. For each breast, place it just in from one edge of the pastry, roll the pastry over the breast and press the two edges of pastry together. Using the tines of a fork, press along the joint to seal it and make it look nice.</p>
<p>5. Brush the pastry with the beaten egg.</p>
<p>6. Cook for 25 minutes, then rest for 10 minutes before eating.</p>