Put the yolks of two fresh eggs into a

From 1922:

Put the yolks of two fresh eggs into a basin with a saltspoonful of salt and half a saltspoonful of pepper. Stir with a wooden spoon, and pour in one gill of good salad oil. Do not use any of the nut oils; pure olive or salad oil is essential. Add this drop by drop, beating well the whole time.
When the oil is absorbed, the mixture will be thick. Add a tablespoonful of vinegar and half a teaspoonful of made mustard. Set on ice or in a cool place till needed.

Another dressing winch is excellent with lobster is not quite so rich, and is preferred by those to whom oil is objectionable: Mix a heaped tablespoonful of butter with the same quantity of flour. Melt gently over the fire in a small saucepan. Then add half a large cup of milk, and boil until thick and smooth. Take off fire, and add a teaspoonful of salt, and when cooled add a beaten egg. Heat again, but do not allow the mixture to boil or it will curdle.
Finally, add a teaspoonful of made mustard, a dessertspoonful of sugar, and three tablespoonfuls of vinegar. The proportions of these seasonings can be regulated according to taste. This dressing will keep in a covered jar for four days.