This irresistibly rich, cool ice cream cake brings together a moist chocolate cake layer with coffee ice cream and chocolate ganache, topped with toffee bits and chopped almonds. It makes a summer birthday party extra-special.
1Preheat the oven to 350°F. Butter a 9-by-13-inch baking dish, line it with parchment so it overhangs two sides, and butter the parchment.
2To make the cake, sift the flour, cocoa, and baking powder into a bowl. Whisk in the sugar and salt. In another bowl, whisk together 3⁄4 cup warm water, the egg, oil, and vanilla until blended. Pour the wet ingredients into the dry ingredients and stir just until blended. The batter will be very thick. Spread the batter into the prepared dish in an even layer. Bake until a toothpick inserted into the center of the cake comes out clean, about 20 minutes. Let cool for 10 minutes in the dish on a wire rack, then remove from the dish and let cool completely. Remove the parchment and return the cake to the dish.
3Put the ice cream in a bowl and stir with a large metal spoon to soften the ice cream until spreadable (make sure it doesn’t get overly soft and soupy). Spread the ice cream over the top of the cake into a thick, even layer. Cover with plastic wrap and freeze until firm, about 2 hours.
4Meanwhile, make the ganache. In the top of a double boiler set over barely simmering water, but not touching the water, stir together the chocolate chips, butter, cream, and corn syrup. Heat, stirring often, just until the chocolate is melted. Add the sifted confectioners’ sugar and vanilla and stir well until smooth. Let cool slightly until cool but still spreadable (if the ganache cools too much, gently warm it until spreadable but not hot).
5Quickly spread the ganache over the ice cream in an even layer. Sprinkle with the toffee bits and almonds. Freeze the cake until firm, about 4 hours. Cut into squares and serve.