Phew...that was a long project! The results were far from perfect, but I think they're cutesy enough to horrify my friends. It's like me to make heart shaped cookies, but it's not like me to make them near Valentine's Day (which I think is simultaneously the most ridiculous holiday and the most brilliant marketting ploy ever).
A few thoughts:
They're pretty, and they taste good, but I need practice.
These don't work unless you have very flat cookies.
These don't work unless you have plenty of filling. I tried to skimp as I ran out of filling, and it led to a lot of cookie cracking.
The filling Becca Porter posted was good in that it allowed me to use lemon juice, zest, and oil. A plain buttercream wouldn't really work with very much juice, and I love the tanginess of lemon juice. Still, I didn't like the taste of shortening and would use butter in the future. I thought the texture from the gelatin was a little strange too; a little more marshmallowy than I'd like and not enough like the inside of an Oreo.
How does it compare to Citizen Cake in San Francisco? The cookies I made were tasty. The filling had a nice tartness to them. However, I'm pretty sure Citizen Cake uses a plain lemon buttercream and their shortbread is a lot softer. Next time I'm going to use a shortbread cookie with cornstarch (it softens the cookie) and a filling that's more like cupcake frosting.