In a medium saute pan, dry toast pasilla peppers over medium heat for a few minutes until you smell the aroma and they soften a bit.
Add onion to dry saute pan and cook until softened and almost charred.
Add butter and garlic and stir, cooking until garlic is translucent, but make sure to not brown the butter.
Add roasted tomatoes and chicken broth.
Cook for about 15 minutes until Pasilla peppers are softened and tender.
Add brown sugar and stir.
Add torn corn tortillas and turn off the heat. Let sit for a few minutes.
Blend with immersion blender until smooth.
Add heavy cream and salt and pepper.
Reheat when ready to serve