Does anyone have a good recipe for millionaire's shortbread ?

[JustinBiebermakesmevom]

I made it last night with the kids and it was bloody awful.....The caramel filling was far too runny and just ran out the side of the cake.

Thanks in advance.

Might not be exactly what you want but ths months good food mag has a billionaires one with peanut butter in. I appreciate if you are allergic to nuts not so good but it made a fabulous billionaires shortbread, made with ready caramelised condensed milk and sugar boiled for a while, it gave various instructions as to how to check it worked :)
Hope that helps, will search it out if I get a chance :)

Here.

Works every time.