In this ice cream cake, both parts—the ice cream (roasted banana) and the cake (chocolate-date)—maintain their identities. Because the cake is frozen completely before a layer of just-churned ice cream is spread on top and the whole pan is sent back into the freezer, you'll get two discrete layers. It's a process that involves a tolerance for delayed gratification you probably never knew you had.
But in the end it means that the cake is complemented, rather than overpowered, by the ice cream—and vice versa. The fudgy, truffle-like texture of the cake stands up to the ice cream but becomes a bit softer; the richness from the dates and the chocolate is more pronounced with the barely-bitter banana flavor as a foil. Rather than icecreamcake, you get ice cream-cake—joint yet separate.
Preheat the oven to 375° F. Line a 9- by 13-inch pan with parchment paper, making sure the parchment hangs over the sides. You'll need to use it as handles later in order to remove the cake from the pan.
Remove the pits from the dates and discard them. In a medium saucepan, combine water and baking soda and bring to a boil. Add the dates to the water, remove from heat, and let soak for 30 minutes.
As the dates soak (and you do want to do this next step as the dates soak, as they should still be warm when they're needed next), use an electric mixer fitted with a paddle attachment to cream the butter and the sugar until fluffy, 3 to 4 minutes. Add the egg and mix until fully incorporated. Add the salt and mix. Add the flour 1/2 cup at a time, mixing until just incorporated.
Drain the dates and add them to the mixture. Add the chocolate and mix until evenly distributed. It will begin to melt into the warm dates—that's good. Transfer the batter (which will be very thick) to the cake pan and spread it with a rubber spatula.
Bake for 15 to 17 minutes, until the center is still gooey and wobbly but the edges are set. Let the cake cool completely in the pan, then wrap it very well with plastic wrap and stick it in the freezer until it is completely frozen.
For the banana ice cream, the chocolate drizzle, and the cake assembly:
When the cake is in the freezer, lower the oven temperature to 350° F. In a baking dish, toss the bananas with raw sugar. Bake until the bananas are very tender and the sugar is bubbling dramatically all around them.
Transfer the bananas to a blender and add the salt, lemon juice, cream, and milk. Blend on high until very well combined.
Chill the mixture until it is very cold, at least 3 hours. I recommend chilling the mixture as your cake freezes.
When the cake is frozen, churn the ice cream according to the manufacturer's instructions. When the ice cream has been churned, spread it onto the frozen cake. Wrap the whole pan very, very well in plastic wrap and send it back into the freezer for at least 3 to 4 hours or, preferably, overnight.
When you're ready to eat the cake, make the magic shell. Add the chocolate to a microwave-safe container with the coconut oil. Melt in 30-second intervals until liquid. Drizzle over the cake and let harden.
Remove the whole cake from the pan using the parchment handles. Let it sit at room temperature for 5 to 10 minutes, until it is soft enough that you can slice it with a knife. Serve with forks.
A (former) student of English, a lover of raisins, a user of comma splices. My spirit animal is an eggplant. I'm probably the person who picked all of the cookie dough out of the cookie dough ice cream. For that, I'm sorry.