Creamy Cheddar and Broccoli Soup

Our sweet neighbors, Amelia and Noah, served this super-yummy soup when they invited us over for dinner.  Now that Soup Season is here (does it really ever end?!), I thought that many of you would enjoy it too!  Serve with a loaf of bread and perhaps a salad and you've got yourself a meal! 

Ingredients:
1 tablespoon butter
1/2 onion, diced

1/4 cup butter
1/4 cup flour
2 cups milk

2 cups chicken stock
2 cups coarsely chopped broccoli florets
1 cup matchstick-cut carrots
1 stalk celery, thinly sliced
2 1/2 cups shredded sharp Cheddar cheese
salt and ground black pepper to taste

Directions:
1. Melt 1 tablespoon butter in a stock pot over medium-high heat. Saute onion until translucent, about 5 minutes.
2. Add the 1/4 c butter to the stock pot; once it is melted, add the flour, whisking until the flour is incorporated and the mixture begins to bubble. 
3. Gradually pour the milk into flour mixture while whisking constantly. Next, stir in the chicken stock. Bring to a simmer until mixture is thickened, about 20 minutes. Add the broccoli, carrots, and celery; simmer until vegetables are tender, about 20 minutes.

4. Stir Cheddar cheese into vegetable mixture until cheese melts. Season with salt and pepper to taste.