I found this recipe at Chockylit's wonderful site Cupcake Bakeshop (you really need to check that out, the woman makes some amazing cupcakes). Her recipe was originally for truffle cupcakes, but I went a little more simple and just made them dark chocolate. Still fabulous – dark, rich, and absolutely lovely. It's almost like a bittersweet-chocolate brownie, except in cupcake form.
Dark Chocolate Cupcakes
3 to 4 oz. Valrhona 85% cacao (or any bittersweet chocolate)
Prepare baking sheets by lining with parchment paper and laying out cupcake cups. Preheat oven to 350 F.
Remove from heat and stir in sugar. Let mixture cool for 10 minutes. Beat in an electric mixer for 3 minutes. Add eggs, one at a time, mixing for 10 seconds between each.