Position a rack in the centre of the oven and preheat oven to 190°C (170°C fan-forced). Line a large rimmed baking tray with baking paper.
In a small frying pan over medium heat, melt 30g butter. Add breadcrumbs and cook, stirring, for 5 mins or until golden. Transfer breadcrumb mixture to a large bowl. Stir in sugar, cinnamon and a pinch of salt. Add the pears and sultanas and stir well to coat.
In a small saucepan over medium heat, melt remaining 80g butter. Lay 1 filo sheet on a work surface with a long side facing you. If necessary, trim to 26cm x 40cm. Brush filo lightly with melted butter. Top with another filo sheet, trimming if necessary, and brush with a little more melted butter. Repeat with 4 more filo sheets and more melted butter to make a stack. Arrange half the pear mixture along 1 long side, leaving a 4cm border at either end. Fold the ends over, then roll up tightly to enclose the filling. Transfer strudel, seam-side down, to the lined tray. Brush with more melted butter. Repeat with the remaining filo sheets, melted butter and pear mixture.
Bake for 45 mins or until dark golden (some juices may spill out). Transfer the tray to a wire rack for 10 mins to cool.
Meanwhile, to make ginger-vanilla custard sauce, in a small saucepan over medium-high heat, bring cream, milk and ginger to a simmer. Set aside for 20 mins to develop the flavours. Whisk the egg yolks and sugar in a medium bowl until blended. Gradually whisk in the warm cream mixture, then return the mixture to the saucepan. Using a flat silicone spatula, stir the mixture over medium-low heat for 5 mins or until the custard thickens (don’t let the custard simmer) and coats the spatula (custard should leave a path on back of the spatula when a finger is drawn across). Strain the custard through a sieve into a bowl. Stir in the vanilla and a pinch of salt.
Gently slide baking paper with warm strudels onto a cutting board. Dust with icing sugar. Using a large serrated knife, trim ends, then cut each strudel into 8 slices. Place on serving plates. Spoon over some ginger-vanilla custard sauce and serve immediately.