This beautiful dessert can be made one day ahead and stored in the freezer, making it ideal for entertaining.
Place the strawberries in a bowl with the icing sugar and mash with a fork until you have a rough pulpy mixture.
Remove the ice cream from the freezer and allow to soften, about 10-15 minutes. Line the base and sides of a 900g loaf tin (about 8.5cm x 19cm x 6cm deep) with clingfilm. Mix the limoncello with half the lemon juice in a bowl and dip the sponge fingers into the mixture, one at a time. Arrange half of the soaked sponge fingers in the base of the tin, so that they run horizontally.
Scoop the ice cream into a bowl and beat in the lemon zest and the rest of the lemon and limoncello juice until smooth; swirl in the lemon curd, softened strawberries and any remaining strawberry syrup to create ripples throughout the ice cream. Spoon half of the ice cream mixture over the sponge fingers; top with the remaining soaked sponge fingers. Spoon over the remaining ice cream mix, smoothing the top. Cover with clingfilm and put in the freezer for at least 4 hours to set completely.
Line a baking tray with baking paper and pop it in the freezer; this helps keep the loaf frozen while you cover it with meringue. Put the egg whites in a large heatproof bowl; add the caster sugar. Set the bowl over a pan of barely simmering water. Whisking constantly with a handheld electric mixer, let the sugar dissolve. As soon as the mixture feels slightly hot on the finger, take the bowl off the heat, whisk vigorously until you have a smooth, stiff meringue – 5 minutes or so. Heat the grill to its highest setting.
Carefully turn out the loaf onto the lined frozen baking tray; discard the clingfilm. Using a palette knife, cover the top and sides of the loaf with the meringue, making swirls on the top. Quickly put under the preheated grill for 30-60 seconds or until just golden. Or use a blowtorch to brown the meringue all over. Cut into thick slices using a serrated knife; serve immediately.