Toast the walnuts and almonds in a dry 24 cm / 10-inch skillet over medium heat for 4 to 5 minutes, shaking often, until fragrant. Tip them onto a plate to cool.

Pulse the figs, raisins, candied peel, Marsala, honey, orange zest and cinnamon in a 2.6 L / 11-cup food processor about 20 times, until a coarse, sticky paste forms. Add the cooled nuts and chocolate and pulse 6 to 8 times, until the nuts are pea-sized. Scrape the filling onto parchment and set aside.

Whisk the flour, sugar, baking powder and salt in a 28 cm / 11-inch bowl. Rub in the cold butter with your fingertips until the mixture looks like coarse sand. Stir in the eggs and lemon zest with a fork, then press into a dough, adding cold water a teaspoon at a time only if it's crumbly. Flatten into a rectangle, wrap and chill for 60 minutes.

Heat the oven to 180 C / 350 F and line a sheet pan (33 x 46 cm / 13 x 18 inch) with parchment. Roll the dough between two sheets of parchment into a 55 x 18 cm rectangle, 5 mm thick, working in sections and patching any gaps with scraps.

Roll the filling into a 55 cm log, about 4 cm thick, and lay it along one long edge of the dough, 2 cm in from the edge. Lift the parchment to fold the dough over the log, trim the overlap and pinch the seam firmly shut. Using the parchment as a sling, set the log seam-side down on the sheet pan, curve it into a ring about 18 cm across and press the ends together.

Beat the egg with the milk and brush it over the ring. Cut shallow slits every 3 cm with a small sharp knife, through the dough only. Bake for 38 to 42 minutes, until the crust is deep golden and firm to the touch.

Warm the jam with 1 tbsp water in a small bowl in the microwave for 20 seconds. Cool the ring on the pan for 15 minutes, brush with the jam and scatter the pistachios. Slide it onto a rack and cool completely, about 60 minutes in all, before slicing with a serrated knife.