Wisconsin Cheddar Beer Soup

4 Tbs unsalted butter
1 onion, minced (about 1 cup)
2 medium garlic cloves, minced
1/3 cup unbleached all-purpose flour
1 3/4 cups low-sodium chicken broth
1 12oz bottle beer
2 cups whole or low-fat milk
12 oz sharp cheddar cheese, shredded (about 3 cups)
4 oz American cheese, shredded (about 1 cup)

You will need one 4 oz chunk of American cheese from the deli counter for this recipe; do not use pre-sliced or packaged shredded cheese here. Freeze the American cheese for 15 minutes to make shredding easier.
2 tsp cornstarch
salt and pepper
popcorn for garnish (optional)

Melt the butter in a large Dutch oven, or pot, over medium heat.
Add onion and carrots and cook until lightly browned, 8 to 10 minutes.
Add the garlic and cook until fragrant, about 30 seconds.
Stir in the flour and cook until golden, about 1 minute.
Slowly whisk in the broth, beer, and milk.
Bring the mixture to a simmer, then reduce the heat to low and simmer gently (do not boil), 20 to 25 minutes.
Meanwhile, toss the shredded cheese and cornstarch in a large bowl until well combined.
Puree the soup in a blender, or food processor, in two batches until completely smooth.
Return to the pot, and simmer over medium-low heat.
Whisk in the cheese mixture, 1 handful at a time, until smooth.
Season with salt and pepper to taste and serve.

"The Best of America's Test Kitchen 2010". Cooks Magazine. April, 2010: page ?.