Add leeks, carrots, garlic, and bay leaf. Cook, stirring occasionally, until vegetables begin to soften (10-12 minutes). Reduce heat to low and sprinkle flour over vegetables, cook, stirring, 1-2 minutes.
Add milk, pale ale and cream, stirring to combine for 5-6 minutes.
Stir in Worcestershire, paprika, salt and pepper. Bring mixture to a simmer over low heat. Cook 20 minutes, stirring frequently.
Add cheese one handful at a time, stirring until melted before adding additional cheese (do not boil).
Discard bay leave.
Spoon into bowls and garnish with crushed pretzels.