Mix the limoncello and lemon juice together and divide between 2 shallow bowls. Dip half the sponge fingers, one at a time into one bowl of limoncello and use the biscuits to line the base of the lined tin. (Drizzle over any unused limoncello to help soften the biscuits).
Mash the ice cream into a bowl. Lightly crush the meringues and add to bowl along with 3 tablespoons of the lemon curd. Mix gently and spread mixture over the sponge fingers (work quickly as you don't want the ice cream to melt).
Dip the remaining sponge fingers in the other bowl of limoncello and arrange on top of the ice cream. Freeze the cake for 2 hours until firm, and then turn out and peel off the clingfilm.
Just before serving, spread the yogurt on top. Drizzle with the last spoonful of lemon curd and swirl lightly together. (If you don't want this eaten all in one sitting freeze half as soon as it's made, wrap it in clingfilm and keep in the freezer).
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