1 12 ounce marble pound cake, such as Entenmann's brand, cut into 1/2-inch-thick slices
1 pint vanilla ice cream, softened
20 chocolate wafers, such as Nabisco brand, plus 4 crushed wafers
1 pint chocolate ice cream, softened
Bring the heavy cream to a boil over intermediate-high heat in a small saucepan. Place the chocolate chips in a heatproof medium bowl and pour the boiling cream over the chocolate. Wait until the chocolate is melted, for 2 minutes. Blend the mixture with a fork for a 2 minutes, until the ganache is smooth.
Line a nonstick 9 x 5 x 3 3/4-inch loaf pan with two overlapping sheets of plastic cover, allowing a 4-inch overhang on all sides.
Pour half of the ganache equally into the lined pan and spread to cover the base. Wrap the ganache with a single layer of strongly packed cake slices; be sure the layer is flat and even.
Spread the vanilla ice cream equally over the pound cake. Wrap the ice cream with a layer made of half of the chocolate wafers. Spread the left out ganache equally over the wafers, then top the ganache with another layer, using all of the left out wafers, and keep the cake in the freezer for about 30 minutes to chill and firm up.
Take out the cake from the freezer and spread the chocolate ice cream over the wafers. Top with an extra flat, single layer of firmly packed slices of pound cake, trimming 1 or 2 slices to fill in the gaps .The cake may be somewhat higher than the pan. Wrap the cake entirely with the plastic overhang and freeze until firm, at least 5 hours or overnight.
To untie the ice cream cake from the pan, open the plastic cover and invert the pan over a flat serving platter. Take away the plastic wrap. Spread the crushed chocolate wafers over the ice cream cake, then slice and serve instantly.