I make a flourless chocolate cake in a 9 inch springform pan, and it only takes 35-40 minutes, so 1/2 hour might be a lot for cupcakes. I would start checking at around 20 minutes, or when you can smell them baking, whichever comes first. The cakes will start to form a thin crust on top when they are done. A flourless chocolate cake should be soft in the middle. If you bake it till the knife comes out clean, it will be over-done. (IMHO)

I looked at another recipie for flourless cupcakes and it says bake for 30 min at 170 degrees celcius but that didnt include alcohol but I'm guessing youre using it for flavour not alcohol

stick a skewer or knife in and make sure it comes out clean otherwise keep it in the oven for a few more mins

I'd keep an eye on them because I dont want you to blame me for burnt cake