Toss the pears with 4 tbsp sherry in a bowl, then cover and leave to steep while you make the meringues.
Heat the oven to 150C/130C fan/gas 2 and line a large baking sheet with baking parchment. To make the meringues, put the egg whites in a very clean bowl and beat with an electric whisk on medium speed for 3-4 mins until white, foamy and doubled in size. Alternatively, use a stand mixer. Increase the speed and add the sugar, 1 tbsp at a time, whisking each addition until completely incorporated before adding another. When all the sugar has been added, beat the mixture for a further 2-3 mins until it’s glossy, shiny and holds stiff peaks on the beaters. Whisk in the vanilla until incorporated.
Spoon six dollops of meringue onto the prepared baking sheet using a large metal spoon, leaving plenty of space between each. Bake for 1 hr 30 mins, then turn off the oven, leave the door slightly ajar and leave the meringues inside to cool to room temperature, about 1-2 hrs (see tip).
Meanwhile, arrange the cake pieces in a large trifle bowl, or divide between eight dessert glasses. Top with the pears, reserving eight slices to decorate, and drizzle over any juices from the bowl. Pour the remaining sherry over the cake and fruit, then chill until ready to assemble.
To serve, whip the cream with the icing sugar using an electric whisk to soft peaks. Crumble four of the meringues and gently fold into the whipped cream, then spoon the mixture over the trifle.
Crumble over the remaining meringues and scatter with the amaretti biscuits and toasted almonds. Top with the reserved pear slices, then serve straightaway or chill until ready to serve – the meringue pieces will start to dissolve and lose their crunch over time, but the trifle will still be delicious for up to 3 hrs.