2) In medium bowl, combine milk, lemon juice, and zest; blend in egg yolks. Divide among the mini pie crusts. Bake for 10 to 12 minutes until the filling is just set, it can still be wobbly in the center when shaken.
3) With an electric mixer, beat egg whites with cream of tartar until soft peaks form. Gradually beat in the sugar until stiff. Transfer the meringue to a piping bag fitted with a medium star tip. Pipe stars of meringue all over the surface of each pie. With a blow torch, carefully brown the meringue on top of the pies.
Note: In the US you can buy pre-made pie crusts made with 'Graham Crackers' which are the equivalent of digestive biscuits. See Giada di Laurentiis' recipe for Graham Cracker Pie Crust.