Line an 8 inch springform pan with parchment. Melt the chocolate chips and coconut oil together, stir in the crushed cookies until coated, then spread on a lined plate and freeze for 15 minutes before breaking into crunchy pieces.
Beat the cream cheese, 1 cup powdered allulose, vanilla extract and salt with 1/4 cup of the heavy cream until smooth. Whip the remaining 2 3/4 cups heavy cream to stiff peaks and fold it in.
Transfer half of the base to a separate bowl. Whisk the cocoa powder with the hot water into a smooth paste and fold it into that half to create the chocolate layer.
Spread the chocolate ice cream into the pan and freeze for 30 minutes until slightly set.
Sprinkle two thirds of the chocolate crunch over the chocolate layer, then spread the vanilla ice cream on top. Cover and freeze for at least 6 hours or overnight.
Whip the 1 cup heavy cream with 3 tablespoons powdered allulose and vanilla extract to stiff peaks.
Release the cake from the pan, frost the top and sides with the whipped cream and press the remaining chocolate crunch around the edges.
Freeze for 30 more minutes to set the frosting, then let it stand for 10 minutes before slicing.