2 medium leeks (white and pale green parts only), cut into 1/4-inch dice (2 cups)
2 medium carrots, cut into 1/4-inch dice (1 cup)
2 celery ribs, cut into 1/4-inch dice (1 cup)
2 teaspoons finely chopped garlic
1 Turkish or 1/2 California bay leaf
1/2 stick (1/4 cup) unsalted butter
1/3 cup all-purpose flour
2 cups whole milk
1 3/4 cups reduced-sodium chicken broth (14 fl oz)
1 (12-oz) bottle ale such as Bass
1 tablespoon Worcestershire sauce
1 teaspoon dry mustard
1 teaspoon salt
1/4 teaspoon black pepper
1 lb extra-sharp Cheddar (preferably English; rind removed if necessary), grated (4 cups)
4 bacon slices (3 1/2 oz total), cooked and crumbled