But here it is anyway, behold the ice cream cake info:
1.) Make the cakes. I made three 9-inch cake layers. I just used the sour cream white cake recipe I always do, which starts with a box mix. He requested blue, so we made it blue. And then I cut off the tops to flatten them, and frozen them in freezer bags for several hours. (Confession: I burned the sh!t out of the first three layers while I was making his birthday video and not paying attention, so I had to do them over the next day. Don't do that.)
2.) Layer with ice cream. I softened some ice cream (half an hour, til you can almost stir it) and layered it with the cakes in an 8-inch springform pan. (The internet told me to do a deep springform one inch smaller than the cake pans, since they shrink a bit when cooking, and you want a tight fit for the springform mold. Do that.) (The internet also told me to put a sheet of parchment paper down in the bottom of the pan before stacking the cakes in, to make it easier to move to a plate later. Do that too.)
The top layer of cake stacked sort of on top of the pan, which was fine. Then I wrapped it all up in saran wrap and froze it for another few hours. I don't have a picture of what that looked like (I only took these pics for soliciting text praise, not recipe posting) ("recipe" hahahaha *wipes tear*) so just use your imagination: top cake layer sticking out on top, it's fine.
3.) Whipped cream frosting. The internet told me (are you sensing a theme here?) to use just whipped cream as frosting that buttercream doesn't taste good with ice cream cake, since it's much sweeter and it's jarring. Also, butter doesn't stick to frozen ice cream very well, because duh.
So I made some whipped cream and sweetened it a bit (a few spoonfuls of powdered sugar) and added some vanilla, and it worked great. I frosted it and stuck it back in the freezer.
4.) Ganache. In one of the ice cream cake videos we watched, Nathan saw one that was finished with a ganache, and he wanted that. But the video was very unhelpful ("and then, frost and top however you like, and serve chilled!") and so I did a LOT of brainstorming on ganache. I needed it thin enough to pour over the top (yet thick enough not to totally run off), yet not so warm that it would make the whipped cream fall apart. And not so sweet that it would taste jarring, like I had been warned about the buttercream.
So! I used bittersweet chocolate, chopped it up super finely so it would melt fast without the cream needing to get too hot, and then I used two parts cream to one part chocolate. And I stirred it while it cooled forever and ever (seriously like an hour) before I poured it over the top. It worked great! Not too sweet, just the right thickness, I give myself an A+.
5.) Sprinkle and serve. I put sprinkles on and put it back in the freezer til it was time to eat. We only thawed it about five minutes before we tried to put candles in, and that wasn't enough. It needs 10-15 minutes at least, to be soft enough to cut and serve.
Nathan loved it; it's exactly what he wanted, so it's a win for that alone.

