1. In a large stockpot, melt butter over low heat. Add onions, potatoes and garlic. Cook until onions are soft, stirring constantly (about 5 minutes). Stir in flour to coat vegetables and to make a light roux. Slowly begin to whisk in the half-and-half, one cup at a time. Let mixture come to a simmer before adding the next cup. 
2. After adding the half-and-half, stir in the tomatoes, corn, stock, thyme, salt, Creole seasoning, black pepper and cayenne. Bring to a low simmer; cook for 15 minutes. Add crawfish. Cook for 10 more minutes, just until crawfish are heated through. Add additional stock to adjust consistency. Garnish with chives, if desired.

Calories: 355, Fat: 23 g (14 g Saturated Fat), Cholesterol: 122 mg, Sodium: 620 mg,  Carbohydrates: 26 g, Fiber: 3 g, Protein: 14 g.