Not shown in video: Brush a 3-quart glass bowl with vegetable oil.
Line the bowl with plastic cling wrap. Layer the bowl with 2 pints of chocolate ice cream and 1 pint of vanilla ice cream. Press and smooth the ice cream with spatula.
Sprinkle the ice cream with chocolate wafer crumbs and press it out with spatula.
Cut the pound cake into 1/2-inch-thick slices. Cover the ice cream completely with the slices, trimming as needed (you'll use about two-thirds of the cake). Cover with plastic wrap and freeze until firm, at least 2 hours or up to 2 days.
For the meringue, whip the egg whites and cream of tartar in a large bowl with a mixer on medium-high speed until foamy, about 2 minutes.
Gradually beat in the sugar on high speed until the whites are glossy and hold stiff peaks.
Remove the top layer of plastic wrap, then invert the cake onto a big plate (if necessary, let the cake stand overturned until it slips out).
Remove the rest of the plastic wrap and cover the ice cream completely with the meringue, making the dome-shaped top slightly thicker than the sides. Form swirly peaks in the meringue using the back of a spoon.
Not shown in video: Freeze for at least 3 more hours.
Preheat the oven to 240 degree Celsius. Bake the frozen cake until the meringue peaks are golden, about 2-4 minutes, or brown the meringue with a blowtorch.
Let the cake soften at room temperature for 5 to 10 minutes before slicing.