Ingredients
Method
- Add the egg yolk, Dijon mustard, and lemon juice or vinegar to a tall, narrow container.
- Pour in all the oil at once — don't stream it in for this method.
- Insert the immersion blender all the way to the bottom of the container. Turn it on and hold it still for several seconds, until the emulsion begins to form at the blade.
- Once the emulsion is established at the bottom, slowly draw the blender upward, pulling the emulsion up through the rest of the oil. This should take about 10-15 seconds total.
- Season with salt to taste.
Notes
Why the oil goes in slowly (for other methods): Egg yolk contains lecithin, a molecule that grabs oil droplets and suspends them in the watery part of the yolk — that's the emulsion. Lecithin can only wrap so many oil droplets at once, which is why methods like the whisk or food processor add oil gradually. The immersion blender is the exception: its blade incorporates oil so fast that it doesn't need to be added slowly.
Why Dijon mustard matters: Mustard isn't just there for flavor. It has its own natural emulsifiers, so it acts as backup insurance for the emulsion — not something to leave out if you want the most reliable result.
Why egg yolk, not a whole egg: The emulsifying power in an egg comes from the yolk. Adding the white brings extra water into the mixture without adding any emulsifying power, which can leave the mayonnaise thinner and less stable.
If your mayonnaise breaks: Crack one fresh egg yolk into a clean bowl, and slowly drizzle the broken mixture into it while whisking — the same way you'd add oil in the first place. The fresh yolk still has emulsifying power the broken batch has already used up. This same fix also works if your mayonnaise turns out thin or runny rather than fully broken.