Guava jam is my all-time favorite and I like to use a thick layer of it for maximum impact. When I have the option, I like to use half Hawaiian Guava (Hawaiian Sun brand usually) and half of a Latin style - the variety that is so thick you can slice it. I put both of those in a food processor and whiz them together until smooth.
However, any type of jam can be used in this recipe. Tart jams tend to be the most well-liked. Blackberry is always a fan favorite but Raspberry is equally good in my opinion. I use seedless whenever possible - Knotts Berry Farm is a good choice. When using Seedless Jam, one 17.5 oz jar should be all you need, volume-wise.
![double-layer guava jam bars](http://pastrygems.com/wp-content/uploads/2015/11/double-layer-guava-jam-bars.jpg)