Ingredients

• 1 large egg
• 1 tablespoon Dijon mustard
• 1 tablespoon vinegar (red or white wine)
• 1/4 teaspoon fine sea salt
• 240ml (ish) vegetable oil
• 1 teaspoon fresh lemon juice (optional but recommended)

Method

1. Add egg to a food processor and blitz for 20 seconds.
2. Add mustard, vinegar, salt - blitz again for another 20 seconds.
3. With oil ready, turn on the food processor (and leave it on).
4. Add oil tablespoon at a time, waiting ~10 seconds for it to fully mix in each time.
5. Add lemon juice + salt to taste.

Notes

• We're assuming you've got a food processor that lets you add liquids while it's running. If you don't, well, it's gonna get tedious.
• The trick to emulsification is adding only small amounts of oil at first, else it will split. Later on larger amounts can be added without much concern.
• Lemon juice is not only tasty, it helps stabilise the mix over time.
• Choice of oil is important. A flavoured oil will functionally work, but yeah, it'll have that flavour. Canola, safflower, or vegetable oils are great. Sunflower or peanut - maybe? Virgin olive oil - no.