Line a 9-inch springform pan with parchment paper.
Put Oreo Cookies in a food processor and blend until they turn into fine crumbs. Pour in melted butter and pulse a few times until well blended.
Pour cookie crumbs into prepared pan and press down into even layer on bottom of pan.
Place pan in freezer for 15 minutes while you prepare the sherbet filling.
Transfer sherbet to a large bowl and let sit at room temperature for about 5 minutes. Give it a quick stir with a wooden spoon or spatula. You want it to be soft enough to spread, but not so soft that the colors are all blending together.
Put the sherbet over the cookie crust and then use the wooden spoon or spatula to smooth it out. Place cake in the fridge for at least 30 minutes.
If using it, pour marshmallow sauce over the top of the sherbet and spread it around to fully cover. Put the cake in the freezer for another 30 minutes.
Spread whipped cream over the marshmallow layer and add on some sprinkles. Cover with plastic wrap or foil and put entire cake back in the freezer for at least 12 hours.
Use a sharp knife to cut cake into slices (be sure to cut through the cookie crust as this will be a bit harder than the rest of the cake).