Curried Potato and Cauliflower Soup with Dumplings

1/4 cup butter
1 large white onion, chopped
4 cups peeled and diced baker potatoes
3 cups chopped cauliflower florets
8 cups chicken stock or water
2 tbs curry powder
kosher salt/fresh ground pepper
1/4 cup sour cream
Melt butter in a stock pot over medium-low heat. Add onions and cook until translucent. Add curry powder and cook 1 minute. Add remaining ingredients, reserving 1 cup of the cauliflower, and bring to a simmer. Cook until vegetables are tender. Puree with a handheld blender. Season to taste. Add remaining cauliflower and return to heat.
For the dumplings:
In a small pot, bring 1 cup water, 2 tbs butter and 1 tsp salt to a boil. Remove from heat. Thoroughly stir in 1 1/3 cups flour. Let cool. Transfer mixture to a large bowl. Stir in two eggs, 1/2 cups chopped parsley or cilantro, 1 tsp ground coriander and 1 tsp pepper.
Drop dumpling batter by teaspoonfuls into simmering soup. Close lid tightly (no peeking!) and cook for 10 minutes. Remove from heat and stir in sour cream.