How many of these little rings do I need for a 15 x 12 x 2" pan? TIA!!
I never use a heating core. I don't want the big hole(s) in my cake. I use greased, inverted metal flower nails. One or two in smaller pans (9" - 12") and more in larger pans. Spread out the nails to evenly spread the heat. The holes left by these nails is way smaller than those left by a heating core. The nail holes are easy to hide with buttercream and/or fondant.
thank you ... I didn't really want to buy the cores, thinking about the holes!!
No problem. There is a tutorial with pictures on here about how to use the flower nails as heating cores. I don't know where it is, but if you do a search for it, you should find it.
Personally, I never use a baking core on that size cake or even on 12x18, and only use rose nails when using WASC batter.
However, for future reference (I know you don't plan to buy a bunch of heating cores) and FYI, to properly use a heating core, you prepare it the same way you prepare the pan. Put it into the pan and pour batter around it, then you fill the heating core 2/3 full with batter. When the cake is done, remove the core. Then pop out the cake from inside the core and insert the "cake plug" into the hole. Presto! No hole!
I don't use any kind of heating core on that size pan, just bake even strips.