Add 8 frosted flakes to a food processor or blender and pulse until coarse crumbs form. 
In a large bowl, melt butter in the microwave on 30-seconds intervals until full melted. 
Add the frosted flakes crumbs and brown sure to the butter and mix until combined.
Line a 9x13-inch pan with parchment paper and sprinkle about half of the mixture over the bottom of the pan, spread out evenly.
Scoop the Nantucket Nutty Cone Sundae Ice Cream over the frosted flakes mixture and use a rubber spatula to spread it out evenly. 
Reserve ½ cup of the frosted flakes mixture and spread the rest out over the top of the ice cream. 
Add heavy cream, powdered sugar, and vanilla to a large bowl and beat on high speed until stiff peaks form. Spread out over the frosted flakes mixture in the pan.