For the semifreddo: Whip the cream to medium stiff peaks and place in the fridge until ready to use.
Melt the chocolates in a microwave dish and set aside.
Whip the egg yolks on medium-high, while you bring the sugar and 1/4 cup water to a boil. Heat the sugar and water to 240 degrees F. With the mixer running, stream the hot sugar syrup into the yolks and beat until cool. Fold in the melted chocolate, then the whipped cream. Spoon into small disposable paper cups, freeze for a few hours, then insert lollipop sticks into the center. Freeze overnight.
For the crumble: Preheat the oven to 325 degrees F.
Combine the butter, graham cracker crumbs, flour, sugar and salt and bake for 12 minutes. Stir and continue baking until dry and toasted and golden brown, another 5 to 7 minutes.
For the meringue: Place the sugar, egg whites and vanilla seeds in a mixing bowl and put over a water bath. Heat until the mixture is warm and the sugar dissolves. Transfer to a stand mixer and beat on medium-high speed until the meringue is thick and creamy, 10 to 15 minutes.
To assemble: Unwrap the pops and roll in the cooled crumble. Place in a styrofoam base or a cup filled with sugar. Pipe or scoop a dollop of meringue on top and toast with a kitchen torch. Serve immediately, or top with meringue, place in the freezer until ready to use and torch right before serving.