Take the chocolate ice cream out of the freezer and allow it to sit at room temperature to soften while making the crust.
Place the sandwich cookies and sugar in the bowl of a large food processor. Pulse until the mixture is a consistent, fine crumb.
36 cream filled chocolate sandwich cookies, 1/2 cup sugar
Add the melted butter to the food processor and pulse until the mixture resembles coarse sand and just starts to clump together.
1/2 cup butter
Reserve about 1 cup of the mixture - you will use this as your filling between the layers of ice cream.
Press the remaining crust mixture in the bottom and slightly up the sides of a 10" spring form pan.
Scoop the chocolate ice cream into the prepared crust. Use an offset spatula to spread the ice cream into an even layer.
1 1/2 qt chocolate ice cream
Crumble the reserved crust mixture over the surface of the chocolate ice cream. Put the pan in the freezer for about two hours or until the chocolate layer is very firm.
About 15 minutes or so before the chocolate layer is done chilling, take the vanilla ice cream out and allow it to sit at room temperature to soften.
1 1/2 qt vanilla ice cream
Scoop the vanilla ice cream over the top of the crust crumbles and chocolate ice cream already in the pan. Use an offset spatula to spread the ice cream into an even layer.
If you are using sprinkles, distribute them in an even layer over the surface of the vanilla ice cream.
sprinkles
Return the pan to the freezer for about four hours or overnight before serving.
Allow the ice cream cake to warm up slightly (about 10-15 minutes are room temperature) before attempting to remove the outer ring of the spring form pan and slicing the cake.
Notes
I like to add up to 1/2 tsp of salt to the crust, I think it helps to balance the sweetness.
You can replace the chocolate and vanilla ice creams with your favorite flavors. I used chocolate moose tracks ice cream in place of the chocolate ice cream and salted caramel ice cream in place of the vanilla ice cream.
You can also play with different flavors of sandwich cookies to compliment the ice cream flavors you choose.
The sprinkles can be any color or shape you like, mix and match to suit the occasion. Since mom often made this for Christmas, I chose to use Christmas themed sprinkles (although, I think she often used traditional rainbow sprinkles)
You can also play with other toppings, like chopped candies (Reese's Peanut Butter Cups, Snickers, Milky Way, Heath Bars, etc.), crushed cookies, chopped brownies or blondies.
If you'd like to give it more of an ice cream sundae feel, you can drizzle some ice cream toppings like hot fudge, caramel, butterscotch, marshmallow, or peanut butter over the crumb mixture between the layers.