Marinate the pork in the soy, honey and mustard for up to 12 hours.
Heat the oven to 200C/400F/Gas 6.
To make the pea purée, place the peas in a blender with a little salt and freshly ground black pepper. Add water to loosen if necessary.
Roll out the puff pastry until it is slightly longer than the pork loin. Brush the edges with the egg wash, using a pastry brush. Fill with the pea purée, and top with the pork.
Roll the pastry round to seal the pork in. Make sure it's completely sealed before cutting the ends off with a knife.
Bake in the oven for 15-20 minutes or until cooked through and the pastry is risen and golden.
Serve.