Line a 1.5 to 2 litre pudding mould or 23cm x13cm loaf tin with cling film, leaving enough overhang to cover the top. Set aside.
In a large microwave-safe bowl, combine pineapple, cherries, sultanas and brandy. Microwave on HIGH for 2 minutes, stirring twice. Let cool completely. (Alternatively, cover and soak fruit at room temperature for 8 hours or overnight).
Soften ice cream in refrigerator for 30 minutes.
Stir pecans and almonds into fruit mixture; stir in ice cream. Pack into prepared mould, smoothing top. Cover with overhang and freeze until solid, about 12 hours.
To serve, let pudding stand in refrigerator for 15 minutes. Using overhang, remove from mould. Dip sharp knife in hot water and wipe dry; slice pudding. Serve with sauce.
To make the Chocolate Orange Sauce: In small saucepan, bring cream and syrup to the boil; add chocolate, liqueur and orange zest, whisking until smooth. Let stand until thickened, about 15 minutes. (Make-ahead: Transfer to airtight container. Place cling film directly on surface; cover and refrigerate for up to 5 days. Reheat before serving).