1. Mix together the oils in a measuring jug.
2. Place the egg yolks, mustard, lemon juice and salt in a food processor and blend until well combined, about 15-20 seconds.
3. With the motor running on a slow speed, very slowly begin to add the oils through the feed tube of the food processor. Once about ¼ of it has been incorporated, you can begin to add the oil a little more quickly. You may need to scrape down the sides of the food processor with a spatula.
4. If the mayonnaise starts to thicken too quickly, add teaspoon or two of hot water before adding the remaining oil.
5. When all the oil has been added, taste for seasoning, adding more salt, lemon juice or a little pepper if desired.
6. Place the mayonnaise into a small airtight container or a small bowl covered with plastic food wrap and refrigerate. The mayonnaise will keep for a week in the refrigerator.

Note: Using olive oil can produce quite a strong taste, so use a greater proportion of vegetable oil if you prefer a milder tasting mayonnaise.

This basic mayonnaise can be flavoured with other ingredients, for example:
- Add garlic to make aioli
- Add grated lime rind and juice to make a lime mayonnaise
- Add capers, gherkins, shallots to for a tartare sauce
- Add fresh herbs to make a herb mayonnaise
- Add wasabi paste to make a wasabi mayonnaise
- Add tomato sauce, Worcestershire sauce and Tabasco for a seafood sauce.

How to fix a broken Mayonnaise
If the mayonnaise becomes “broken”, you will have a grainy, thin liquid rather than a thick, glossy sauce.

This can be easily fixed, so there’s no need to throw the mixture out. Start with a fresh egg yolk in the food processor bowl which has been cleaned, and process for 10 seconds. Instead of adding oil, very slowly add the broken mixture until the mayonnaise is strong and stable. You can then add the rest of the broken mixture in a thin steady stream.