The Dulce de Leche ice cream on brownies is my go to "nice" easy to make ahead dessert...
1) Use a different brownie recipe, the one written is dry which makes it very hard to cut the cake. I sub the Supernatural brownie recipe now, but any favorite that's made for an 8x8 pan should do it.
2) Hagen Daz makes the Dulce de Leche ice cream, in fact I just bought some 2 days ago. Just grab a pint at most grocery stores.
The Dulce de Leche ice cream cake is very good, it's really easy, mostly it just takes time to freeze between layers, and it makes a nice presentation. I've used it for birthdays before and it's a crowd pleaser. I would've added it to Richard's thread above, but it's not officially a cake.
I say go for it!!!