In a small deep bowl, mix the two mustards, sugar and vinegar to a paste.
2
With a wire whisk, slowly beat in the oil until it forms a thick mayonnaise-like emulsion.
3
Stir in the chopped dill.
4
The sauce may be kept refrigerated in a tightly covered jar for several days, but will probably need to be shaken vigorously or beaten with a whisk to remix the ingredients before serving it again.
