Cut pork into thinnish slices then into small pieces. Heat 2 Tbsp oil in a large frying pan over a high heat. When hot, add the pork pieces and brown very quickly, then transfer to a plate. Add onion and red pepper to pan, lower heat and pour in any meat juices that have accumulated on the plate from the pork. Season with ¾ tsp salt. Cook gently until tender. Add garlic, sage and olives, then tip everything onto plate with pork.
Cool pan and wipe out. Add remaining 1½ Tbsp olive oil to pan, increase heat to medium-high and when oil is hot, add mushrooms, cut side down. Cook until brown without stirring. Turn mushrooms with tongs and cook for a few minutes more. Season with ½ tsp salt and return meat and vegetables to pan. Stir in crème fraîche.
Roll out pastry until 24cm wide x 48cm long. Cut into 2 pieces – one 27cm long for the lattice top, the other 21cm long for the pie base. Roll the base more thinly until it is the same size as the other piece. Chill both pieces for 10-15 minutes, until firm. Preheat oven to 210°C fanbake.
Put the thinner base piece of pastry on a baking sheet lined with baking paper. Spoon on the filling, keeping it in a little from the edges. Dampen pastry edges with a little water. Lightly dust the other piece of pastry with flour and fold it in half lengthways. Using a very sharp knife dipped in flour, cut ribbons across the pastry through the folded centre but not quite to the edge. Open out the pasty carefully and place it on top of the pork filling. Press the pastry edges together firmly to seal. Use a small sharp knife to lightly cut the edges of the pastry. This opens up the layers without breaking the seal, allowing the pastry to rise and flake. Brush pastry top with beaten egg.
Bake for 20 minutes, then lower heat to 190°C and cook for a further 10 or so minutes until the pastry is a good golden brown. Slide jalousie onto a board and serve hot.
A jalousie is a slatted window and gives its name to pies which have a pastry lattice top. To remove the silverskin (the thin membrane on the outside of the pork) put the blade of a small sharp knife between the meat and silverskin and slide it along to release silverskin.
Article from the May, 2012 issue of Taste magazine.