Ground vs Dried Peppers
I am making this recipe http://www.chow.com/recipes/10646 which calls for ground pasilla peppers. I was only able to find whole peppers, and I plan to grind them in my coffee grinder or blender. But the question is: do I remove the seeds?
I would say, yes, remove the seeds. They could add bitterness.
I read the recipe and it may be encouraging you to perform a unnecessary step (grinding dry chiles).
IMO you get better chile texture and flavor if you put the dry, toasted, whole chiles into boiling water, remove from heat and let steep for maybe 30 minutes. Blend and, if necessary, strain big chunks of skin out. This sauce can be added to the recipe or stored for later use.
BTW pasilla is an abused term here in California. Here anchos (dried poblanos) are labeled 'pasilla' and pasillas (dried chilacas) are labeled 'negro'. Easy to tell the difference - anchos are wider and shorter, pasillas (negros) are longer and narrow. Anchos are usually mild and pasillas are hotter (but not much).
'ancho' is just the Spanish word for wide. 'pasilla' is derived from 'pasa', raisin, 'negro' is black.
The other way to use these whole peppers is to soak them and collect the pulp. I remove the seeds before soaking. They may also be toasted before soaking. The pulp can be scraped off the skin, or the whole mess can be put through a blender and then strained. I like using a food mill.
I grind my own chiles and always take out the seeds (though I'm not fanatical about getting every last one). While the seeds are great to keep in fresh hot chiles, I think they are a bit bitter and don't add any chile flavor when they are from dried versions. They are easy to shake out after you toast and before you grind.