1. Preheat the oven to 350°F (180°C). Heat the oil in a medium saucepan over medium heat. Add the spinach, cover, and cook about 5 minutes, until tender. Drain well and let cool. Pulse the spinach, scallions, smoked chicken, créme fraîche, tarragon, mustard, and lemon zest in a food processor until coarsely chopped. Stir in the pine nuts and season with pepper.

2. Line a baking sheet with wax paper. Place 1 filo sheet on the work surface, with the short side running horizontally. Cover the remaining filo with a damp paper towel to prevent drying. Brush the filo sheet with melted butter. Top with a second sheet and brush again with butter. Cut the filo pastry into three 4in (10cm) strips. Place a heaping spoonful of the chicken mixture about ½ in (13mm) below the top of a strip. Fold the right corner of the strip diagonally to the left to form a triangle that covers the filling. Fold the triangle with the filling down, and repeat folding down and over until you reach the end of the strip. Brush with butter and place on the baking sheet. Repeat with the other 3 strips, then with 2 more filo sheets and the remaining filling. Sprinkle with the Parmesan.

3. Transfer to a lightly oiled baking sheet. Bake for 20 minutes, until golden brown. Serve hot or warm.