How to Make It
In a medium saucepan, combine the cream, peanut butter and salt and bring just to a boil, and then pour over the chocolate in a medium bowl. Let sit for 1 minute to melt the chocolate and then stir until smooth.
Let the vanilla ice cream soften, about 10 minutes. Meanwhile, line an 8-inch round cake pan with plastic wrap, allowing for plenty of overhang. Spread the vanilla ice cream in the pan in an even layer. In a bowl, stir 1/2 cup of the chopped peanuts with 3/4 cup of the ganache and spread over the top and freeze until firm, at least 2 hours.
Let the chocolate-peanut butter ice cream soften, about 10 minutes. Spread the ice cream over the ganache in an even layer. Cover with the overhanging plastic wrap and freeze until set, at least 2 hours.
Meanwhile, spread the remaining 1/2 cup chopped peanuts in an even layer on a sheet of foil so the peanuts are all touching. Bring the sugar, honey and water to a boil in a small saucepan over high heat. Cook, swirling the pan often, until the sugar syrup turns a light amber color, about 5 minutes. Remove the pan from the heat and stir in the baking soda. As soon as the mixture turns pale and large bubbles form, pour it evenly over the peanuts; do not smooth or spread it out. Set aside until cooled and hardened, then break into 1 1/2-inch pieces.
Remove the cake from the freezer, unwrap and invert onto a cake stand or platter. Pour the remaining cooled ganache over the top of the cake, letting it drip down the sides, and then top with the peanut honeycomb. Sprinkle with sea salt and freeze until ready to serve.