1 large egg yolk
1 teaspoon Dijon mustard
1 tablespoon lemon juice or white vinegar
1 cup neutral oil
1/4 teaspoon salt
Optional: pinch of sugar or pepper
Whisk the egg yolk, mustard, lemon juice or vinegar, and salt in a bowl
Add the oil very slowly, a few drops at a time, while whisking constantly
Once the mixture starts to thicken, add the oil in a thin steady stream
Keep whisking until the mayonnaise is thick and smooth
Taste and adjust with more salt, lemon juice, or mustard if needed
Store in a covered container in the refrigerator