Heat the oven to 180°C/350°F/Gas Mark 4.
Cut the butter in pieces in a saucepan and melt it gently over low heat. Stir in the flour to form a roux and cook for 2 minutes. Slowly pour the milk and stir until thickened. Remove from heat.
Drain and flake crab meat finely, removing any shell. Add the egg yolks, curry powder, salt and pepper. Whisk the egg whites until stiff with a pinch of salt and gently fold into the crab meat mixture.
Butter four individual deep ramekins or soufflé moulds and tie nonstick baking paper to form a wall around the outside. Fill each mould ¾ full with the crab mixture. Bake for 20 minutes. Do not open the oven door once cooking starts or the soufflés will collapse.
Serve immediately garnished with green peppers and chili flakes.