1 egg yolk (or 1 whole egg)
1–2 tbsp lemon juice or vinegar
1 cup neutral oil (canola, sunflower, or light olive oil)
1/2 tsp salt
1 tsp Dijon mustard (optional)
1/4 tsp black pepper (optional)
Add egg yolk, lemon juice (or vinegar), salt, and mustard (if using) to a bowl
Whisk until thickened and fully combined
Slowly drizzle in oil while whisking continuously until the mixture thickens
Continue adding oil gradually until desired thickness is reached
Taste and adjust salt and lemon/vinegar as needed
If using a blender or immersion blender: add yolk, lemon juice, salt, and mustard to the container first
Pour oil on top without mixing initially
Blend at the bottom until thick, then lift and tilt to finish emulsifying
Transfer to a clean jar and refrigerate up to 3–4 days