In a medium-large stock pot, heat vegetable oil, and sauté chopped onions for about 2-3 minutes, until they are transparent, add garlic (if using) and sauté for another minute. Then add beans, water, salt and black pepper and bring to a boil then reduce heat. Simmer for about 20-25 minutes, until the beans are tender. Then add the dill.
Roux: using a medium skillet, over medium heat, add melt butter, add flour, sweet paprika and whisk until well combined. Then add ladles of the soup broth, and whisk until smooth. Then slowly add to the soup, and whisking at the same time.
In a small bowl, whisk sour cream and a couple of ladles at a time up to about 1/4 cup of the hot liquid from the soup. This will help to avoid the sour cream from curdling when adding it into the soup. Then add the sour cream mixture to the soup and bring soup to a slow boil. Whisking until all ingredients are combined and simmer for about 3-5 minutes until soup thickens, and you should have a smooth creamy consistency.
This soup is very tasty served hot or cold with crusty bread. Garnish with fresh dill, chopped scallions and sour cream if desired.
