In a large saucepan over medium heat, melt butter.

Cook onion in butter until softened.

Stir in potatoes and broth, bring to a boil, then cover, reduce heat and simmer 15 to 20 minutes, until potatoes are tender.

2.

Puree potato mixture in a blender or food processor or using an immersion blender; return to pot over medium heat.

Stir in cream, cheese, dill, pepper, salt and cayenne.

Bring to a low boil and cook, stirring, until thickened, 5 minutes.