Heat the oil in a frying pan and fry the medallions for approx. 1 1/2 mins. on each side, remove, season.
Mix the sausage meat, lemon juice, pistachios and parsley, season.
To assemble and bake
Carefully unfold the pastry sheets, brush each sheet of pastry with a little oil, stack the sheets on top of each other, cut into four equal-sized pieces. Place two slices of bacon crosswise in the centre of each piece of pastry, place one medallion on top of each and cover with the filling. Pull the corners of the pastry upwards and press together. Brush each parcel with a little oil.
Bake for approx. 15 mins. in the lower half of an oven preheated to 200°C. Remove, leave to rest for approx. 5 mins., brush with the remaining oil.