Ice cream sundae bombe with a cookies and cream chocolate shell and a ganache topping

Line a two quart metal bowl with two crisscrossed pieces of foil, smoothing it carefully into all the contours of the bowl.

Pour seven cups of water into the lined bowl and mark the water line with a piece of tape. That mark is the guide for how tall the chocolate shell goes.

Put the lined bowl in the freezer. A cold metal bowl increases your working time while you form the shell, and keep the ice cream frozen until you are ready to assemble.

Toast the almonds in a 350F oven until golden brown and let them cool.

Transfer the cookies to a resealable bag, press out the air and seal it, then beat them with the bottom of a heavy saucepan or a rolling pin to coarse crumbs with some larger pieces still in there.

Cut straight down through the paper ice cream carton with a sturdy chef knife, halve and quarter it, and drop the pieces of chocolate ice cream into a large bowl. With a plastic carton, scoop it out instead.

Work the ice cream against the sides of the bowl with something rigid, not flexible, until it is spreadable but not melted, incorporating the cookie crumbs evenly as you go. You are racing the clock; ice cream that melts and refreezes loses its smooth creamy texture and turns icy.

Scrape three quarters of the mixture into the frozen bowl and put the remaining quarter into a container in the freezer for the top.

Spread the chocolate mixture over the bottom of the bowl and up the sides, following the shape, right up to the tape line. If it gets too melty to hold its shape, put it in the freezer for 10 minutes and come back to it.

Freeze the shell solid before filling, about an hour.

Cut through the vanilla pints the same way and work the ice cream just until spreadable, then fold in the rinsed and dried cherries and the toasted almonds until well combined.

Scrape the vanilla mixture inside the frozen chocolate shell, avoiding big air pockets, filling it right to the top of the chocolate layer at the seven cup mark, and level the surface.

Freeze two hours, until the surface of the vanilla is firm.

Work the reserved quarter of the chocolate mixture spreadable and spread it over the vanilla in a thin even layer, as flat as possible because it becomes the bottom of the bombe.

Freeze another hour so the top layer sets and the centre firms up. Freeze the serving plate too.

For the ganache, pour a quarter cup of the cream into a small saucepan and bring it to a gentle simmer over medium to medium-low. Put the chocolate in a small bowl with a pinch of salt if you like.

Pull the cream off the heat and let it cool a few seconds before pouring it over the chocolate, or very hot cream will break it. Let it sit a few minutes, then stir from the centre out without working air in, to a smooth glossy mixture. Set it aside to cool a little.

Unmold the bombe: set the frozen serving plate upside down over the bowl, invert them together, tug down on the foil and peel it off.

Smooth any rough areas left by wrinkles in the foil with a small spatula.

Pour the cooled ganache over the highest point of the dome so it makes big drips down the sides, then finish with sprinkles and put it straight back in the freezer at least 15 minutes to harden.

Whip the remaining cup of cream.

Slice the bombe. If it is very hard, dip the knife in hot water and dry it off first. Serve each slice with a dollop of whipped cream.