Line the bottoms of 2 1/4 cup ramekins with rounds of wax paper, butter the wax paper, and dust the ramekins with walnuts, shaking out the excess. In a small heavy saucepan melt the 1/2 stick butter over moderately low heat, stir in the flour, and cook the roux, stirring, for 3 minutes. Remove the pan from the heat, add the milk, scalded, in a stream, whisking until the mixture is thick and smooth, and simmer the mixture, whisking, for 3 minutes. Transfer the mixture to a bowl, let it cool for 5 minutes, and whisk in the cheddar, the salt, the mustard, the yolks, and the chives, whisking until the mixture is smooth.
In a bowl with an electric mixer beat the whites with a pinch of salt until they just hold stiff peaks, stir one fourth of them into the cheddar mixture, and fold in the remaining whites gently but thoroughly. Spoon the mixture into the ramekins and bake the souffles in the middle of a preheated 400 degrees F. oven for 15 to 20 minutes, or until they are puffed and golden. Let the souffles cool (they will fall). Run a sharp small knife around the edge of each ramekin, invert the souffles into the palm of the hand, and remove the rounds of wax paper. These souffles may be prepared 1 day in advance.
Recipe courtesy of Gourmet Magazine