Note that Finnish eggs are among the safest in the world to be eaten uncooked. To find out why, read here.

1 large or 2 small egg yolks
pinch of salt
pinch of white pepper
1 tsp - ½ tbsp Dijon mustard
250 ml light-tasting oil (turnip rape, sunflower, grapeseed, peanut or corn oil)
½ tbsp tarragon vinegar or juice of ¼ lemon

Bring all the ingredients to room temperature. Lightly whisk together  —  by hand  —  the egg yolk(s), salt, pepper and mustard. Mustard can be omitted. When the mixture starts to thicken, start adding the oil, drop by drop, whisking continually  —  with an electric mixer, if preferred.

When the mixture begins to thicken and emulsify, you can start adding the remaining oil in a thin stream, whisking continually. Finally whisk in the vinegar or lemon juice. Store the mayonnaise in tightly closed jar in refrigerator.

If the ingredients are of different temperature or too cold, or if the oil is added to the egg yolks too quickly, the mayonnaise may separate. This can be fixed in a number of ways listed below:

How to fix separated (curdled) mayonnaise:

1. Whisk in 1 teaspoon of cold water to the curdled mayonnaise, or if that does not help:
2. Mix 1 teaspoon of mustard and 1 teaspoon of the curdled mayonnaise until creamy. Add the remaining mayonnaise to this mixture, whisking it in little at a time.
3. Whisk together 1 egg yolk, pinch of mustard and a few drops of vinegar or water. Add the curdled mayonnaise to this mixture, whisking it in little at a time.
4. In 1 tablespoon of cold water or wine vinegar, mix a little of the curdled mayonnaise. Add the remaining mayonnaise to this mixture, whisking it in little at a time.
5. Whisk 1 egg yolk and add the curdled mayonnaise to it, whisking it in little at a time. Continue whisking and add a little cold water to make the mayonnaise as thin as it was originally.

See a recipe for an easier, foolproof hand blender mayonnaise.

Recipe source: adapted from "Majoneesi", Ihatsu, A. et al., ed. (1993) Otavan suuri keittokirja. Keuruu: Otava and traditional recipes.