You can really make this cake two ways:
Ice cream, fudgy cookie layer, ice cream (like Smitten kitchen)
|Smitten Kitchen - Hot Fudge Sundae Cake|
Either way would be divine as long as you pick compatible flavors.
My sister chose chocolate cake and peanut butter cup ice cream.
So I started making the cake the day before I needed it to ensure I had enjoy cooling time for the cake and refreezing time for the ice cream layer. I would advise starting around 18-24 hrs prior to the end time for your cake.
Step One - Cake Layer
Even though I didn't really want to, I ended up shelling out the big bucks ($4) for a gluten-free devil's food cake mix for the cake part. I wanted to make it from scratch but I was on a limited time frame and my kitchen had been torn apart from the window replacement surgery happening on our house.
The one thing that i would change about the cake over all is the ratio, you really want an even or slightly higher ice cream to cake ratio. That might just be me, but we ended up with a higher cake to ice cream ratio and found it lacking a little. When you go to bake your cake portion, make sure to only fill your cake pan (or pans or cupcake pans) 1/4 of the way full. Trust me. I know it doesn't sound like a lot and it will cause you to have remaining batter, but you really want to make sure that after the cake rises there is enough room to add the ice cream. Bake the cake layer for a little less time because it is less thick. When the knife, fork, toothpick, whatever goes out clean - let the cake cool completely and start smashing Oreos with a rolling pin.
Step Two - Fudgy Cookie Layer
SmittenKitchen has an amazing hot fudge syrup recipe on this link to add her homemade chocolate smashed up cookies. I used homemade hot fudge sauce I already had in the fridge and you can definitely use the ice cream hot fudge sauce you get in a jar from the store. Just watch out for the High Fructose Corn Syrup, it's a killer. But seriously. Then I took about half of the bag of Oreo's (not GF - you caught me) and they got ziploc'd and smashed to smitherin's. Smittenkitchen recommends using a food processor to get them properly crushed and pulverized but i found a rolling pin was much more theraputic. Mix about a half cup of hot fudge and about 3/4 cup of Oreo crumbs together. You want the consistency to still be kind of like frosting so that it will spread nicely on top of your cake and not rip off the top layer. Then once the cake is cool, spread the fudgy cookie mixture on top making sure to spread it thin enough that it makes a thin line between the two layers and doesn't become a layer itself. Unless you want it that way. It could be good like that. I ended up with some fudgy cookie mixture left over (which will go great on vanilla ice cream later) so don't feel like you have to use it all. Then put in the freezer for about an hour so the hot fudge will set.
Step Three - Ice Cream Layer
This is really the only tricky part of the whole cake because you want the ice cream to sit out on your counter for long enough to make it spreadable, but not too liquidy that it will spill all over the cake. Freezing the hot fudge layer makes it a protectant against the ice cream so the cake doesn't get soggy, but the ice cream can spill down around the sides of the cake so be careful not to let it get too melty before applying it.
I found that using the back of a large soup spoon worked the best to spread the ice cream. I also kept a bowl of warm water next to the cake and would dip my spoon in it to keep it from sticking and it spread a lot better that way.
I tried to stack my ice cream layer as high as the pan and as flat as possible. If you can't get it even or as high as you want, don't fret. Getting it done quickly so it can refreeze is much more important otherwise it will all melt and get harder to work with. Once this layer if frozen, you can try to go back and add more if you want.
Step Four - Decorations
To decorate my sister's cake, I just whipped up some heavy cream and piped it in circles around the edge, topped off the circles with Reese's pieces. We put a candle in it right before it was time to sing. You can decorate it however you want. Use whipped cream as a frosting or pipe frosting letters on there.
Step Five - Eating
It was delicious. I do recommend letting it thaw a little before trying to cut it or eat it as the cake hardens a little more than the ice cream. But I was amazed at how good it was! It will definitely be on the rotation for birthday cake ideas!
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