Cappuccino-froth corn soup

Melt butter until foaming. Add onion and garlic purée and cook until softened.
Add mealie kernels and cook for 5 to 6 minutes. Add stock, bring to boil, then reduce heat and simmer for 30 to 40 minutes, or until mealie kernels are tender (15 to 20 minutes if using canned frozen corn).
Purée in a food processor fitted with a steel blade, then pass through a strainer, season with salt and pepper and thicken or thin the soup, if desired.
Cool soup on ice.
Add crème fraîche and whisk furiously with a hand-held blender until frothy.
Ladle into soup cups with lots of froth on top. Sprinkle crayfish, and then chives over. Serve immediately.