1/2 c. dry mustard
1/2 c. white vinegar
1 egg
1/3 c. white sugar
1 pinch salt
1 c. mayonnaise

Mix mustard and vinegar and let stand overnight. Beat egg, add sugar and salt, then add to mustard vinegar mix. Cook over low heat until thick stirring constantly. Let cool thoroughly, then blend in the 1 cup mayonnaise.

Delicious on meat or sandwiches.