When ready to assemble, cut out a cardboard cake round to fit the silicone mold or steel bowl. Use that cardboard to cut the cake to the right size. Use a super silver knife to cut the cake to the right thickness.
Place the cake over the ice cream, cover, then freeze until the ice cream is solid.
To unfold, place the cardboard on the cake, then flip and ease the cake out. If you are using a metal bowl, you'll need to warm the bottom just slightly and ease it out. Place it on a revolving cake stand.
Cover the ice cream in a thick layer of meringue. Take a blob of meringue in your fingers and pull up spikes. This is messy fun, don't try to do this without getting your hands in there! You can freeze the baked Alaska at this stage for several hours or even overnight.
Just before serving, torch the meringue. Serve right away or freeze until you're ready. Use a thin bladed knife dipped in HOT water to slice.