So my sister-in-law LOVES ice cream & her birthday is in a few days, so I'm making her an ice cream cake. Problem is, I've never made one before. So... I got the jist of how to do it, I just have a couple questions.

1) Is there a way to get those chocolate "crunchies" that Carvel cakes have? Maybe use crushed up Oreos or something?

2) I know I'd have to use whipped cream frosting, but I was wondering how I could pipe on it? Can I use the whipped cream thickened & how would I thicken it? Or could I use piping gel or buttercream?

This is how I have made mine in the past. Bake (I will use 8 inch for example) two 8-inch layers. Level and freeze them wrapped tightly to prevent freezer burn or tastes. Line an 8 inch cake pan with plastic wrap and leave extra over hang to use to wrap it up. Soften the ice cream a bit to make it easy to smooth out in the pan. Fill the pan to the top making sure there are no holes or unfilled spaces. Level the top of the ice cream so it will sit flat on the cake layer. Bring up the extra plastice wrap to cover and place in the freezer. I use buttercream on my ice cream cakes and have rave reviews of the added sweetness. Oreos would work well but they won't remain crunchy. When ready to assemble, the ice cream layer is easily removed from the pan and placed between the two cake layers. Frost and place back in the freezer in a tightly wrapped box. I would suggest decorating it just before it is served if the decorations are a different color from the cake. But if you can't wait keep the cake frozen until it is about to be served to prevent running of the colors when it defrosts. Hope this helps. Trick is to keep it frozen so many trips back and forth while decorating may be needed.

I made one last month.

I baked a 1 1/2" white 9x13 cake and also a chocolate cake with the same dimensions. Froze them overnight, then leveled it. I bought a box of ice cream so that I was able to unwrap the ice cream, then slice it into 1" wide slices. I laid out my white cake, put a layer of ganache down (this is where you could do the oreo cookies, too), then put my slices of ice cream down. I had to arrange them so they fit just right, and I had enough ice cream to do a 2nd layer and then some to eat later that night.

Covered the ice cream with the chocolate cake then let it freeze about 1/2 hour. Quickly spread thinned buttercream around, smoothed it as best as I could because the cold cake/ice cream started to firm up the buttercream. But it turned out awesome! I made a frozen BC transfer to decorate the top of the cake and then just piped on the sides and border. Always put it in the freezer between steps for about 15-30 minutes.

I have a no-bake version: Using a 9x13 pan, line with slightly softened ice cream sandwiches, spread 1/2 8 oz. container of cool whip, another layer of ice cream sandwiches, and the remaining cool whip. Freeze for several hours and serve. It tastes just like a Carvel cake.
This uses about 20 ice cream sandwiches, and you can put crunchies in between, caramel, anything - it's delicious!