Melt butter or chicken fat in a Dutch oven over medium heat.

Add finely chopped onion and chopped leek and sweat until tender, stirring often.

Sprinkle in flour and stir well to incorporate.

Cook for 3-4 minutes to eliminate the raw-flour taste.

Whisk in chicken broth and white wine until smooth.

Add carrots cut into julienne strips.

Bring to a boil and simmer for 15-20 minutes, until soup thickens.

Remove from heat and add grated cheddar cheese, Worcestershire sauce, cayenne pepper, and salt.

Stir until cheese is melted and soup is smooth.

Stir in heavy cream and cook until just heated through, without boiling.

Garnish with chopped chives and serve.