Cheddar Ale Soup

1 large onion, chopped
1/2 stick (1/4 cup) unsalted butter
1/3 cup all-purpose flour
2 cups whole milk
1 3/4 cups chicken broth
1 12-oz bottle ale such as Bass
sea salt to taste
white pepper to taste
¼ teaspoon turmeric
1 lb sharp cheddar, grated (4 cups)

1. Cook onion in butter in a large heavy saucepan over medium heat, stirring occasionally, until softened, about 7 minutes. Reduce heat to low and sprinkle flour over onion, then cook, stirring occasionally, for 3 minutes.
2. Whisk in milk, broth, and beer and bring to a simmer; whisk occasionally for 5 minutes. Stir in turmeric, salt, and pepper.
3. Blend until smooth using an immersion blender. Add cheese by handfuls, stirring constantly, and cook until cheese is melted, 3 to 4 minutes (do not boil).