What do you mean by dark chocolate? Baking chocolate? Sweet, Semi-sweet, bittersweet, unsweetened?

Use a high-quality semi-sweet or bittersweet chocolate, around 60-70%. Don't use chocolate chips or baking chocolate. Valrhona, Theo, Guittard, Callebaut are all good choices.

Dark chocolate usually means bittersweet, not unsweetened nor Baker's chocolate.

Dark chocolate is generally a reference to bittersweet chocolate, at least 60%
I'm not sure exactly what Alice meant, but I made this wonderful pudding last weekend with 72% chocolate, and it was fabulous.