Aunt Linda's Mushroom Soup

I'm well aware that my aunt found this recipe somewhere and didn't invent it herself, but it will forever remind me of our cozy, Christmas party at her house where I fell in love with this soup.

I don't have an actual picture- it doesn't matter. It's not what it looks like that makes it appetizing. But here are some cutie mushrooms that will soon be soup:

Mushroom Soup

5 TB butter, divided
2 leeks, rinsed and chopped
2 large carrots, chopped
6 C chicken broth
2 tsp dill (dried is perfect)
2 tsp salt
1/8 tsp black pepper
1 bay leaf
2 lbs of potatoes, peeled, rinsed and cubed
1 lb fresh mushrooms rinsed and sliced
1/2 C heavy cream
1/4 C flour

Melt 3 TB of the butter in a large sauce pan over med heat. Mix in leeks and carrots, cook for 5 minutes or until softened. 
Pour in the broth and season with dill, salt and pepper. Add bay leaf and potatoes and cover, cook for 20 minutes, or until potatoes are soft. 
While that is cooking, saute the mushrooms in the rest of the butter and season with a bit of salt. Add the mushrooms to the soup and cook for another 5 minutes. In a small bowl mix the cream and the flour till smooth, stir it into the soup and serve very warm. 
Garnish with dill.