Crack an egg into a pint-sized wide-mouth Mason jar.
Add mustard, salt, lemon juice and white vinegar.
Add oil on top and allow it to sit for a few seconds so the ingredients separate and the oil floats on top.
Gently place your immersion blender into the jar until it's to the bottom.
Turn the immersion blender on and leave it at the bottom until the mayonnaise begins to emulsify.
Slowly bring the immersion blender up and back down, incorporating the remaining oil until all the contents are thick, creamy and completely emulsified.
Add a lid to the jar and store it in the refrigerator for up to two weeks (see my tips on storing below).
Notes
FAQs:
Why is My Mayonnaise Runny? If you get runny mayonnaise, this means it didn’t emulsify properly and is referred to as “broken mayonnaise”. This is why it’s very important to use mustard, vinegar, and lemon juice. All three have properties that will help with the emulsification process. The other thing is to be sure, when placing the immersion blender inside your cup, that you get it all the way to the bottom and don’t lift it up until you see the mayonnaise has emulsified.
Can I Fix Broken Mayonnaise? Yes, rest assured if your mayonnaise doesn’t emulsify properly, you can save it. All you need is either a teaspoon of mustard or an egg yolk. Add the mustard or the egg yolk into a large bowl and whisk. Continue whisking while adding in the broken mayo until it’s emulsified. Though now that I’ve found this particular recipe combination, I have to say I haven’t had my mayonnaise break on me since! Oh, that I had learned this ten years ago!
How to Store Mayonnaise - Store your homemade mayonnaise recipe in the refrigerator.
How Long Will Homemade Mayonnaise Last? If you’re anything like my family, your mayonnaise will be gone far before it goes bad. But generally speaking, because we’ve added in fermented lemon juice (which will increase the shelf-life) it will last upwards of two weeks in the refrigerator. Some people will tell you because it includes raw egg that it needs to be consumed within five days. This is a judgment call and we’ve never had issues with ours. However, this is also why I like to make smaller batches, so I don’t have to toss a large batch should it go bad before we’re done using it. A tip for keeping your mayonnaise from spoiling is always to use a clean utensil when dipping it into the jar. Any food particles that get into the jar will cause the mayo to spoil faster.