From 1911:
About one tablespoon of evaporated cream, add oil slowly, stirring well all the time; after it thickens add one quarter teaspoon made mustard and salt to taste; then thin out with lemon juice or vinegar.
If the cream and oil do not assimilate quickly and thicken, by adding the mustard this may be counteracted.
This makes a delicious, creamy dressing and can be made thick enough to slice, if so desired, by adding enough oil.