Share 'Spicy dark chocolate bars?'

I searched the forum for a recipe with negative results. Now that I've got tempering more or less under control (maybe and with John DePaula's help) and my chocolate covered Macadamia nuts are working, I'd like to branch out. Can anyone tell me a proper way to add heat to dark chocolate? Heat as in hot and spicy. I've tasted some dark chocolate bars with heat in them and like them. How do you ma…