Add all ingredients in the order listed into a wide-mouth pint Mason jar (or any other jar wide enough to fit an immersion blender).
While the immersion blender is off, place the blade all the way on the bottom of the jar. Turn the immersion blender on low, and let sit on the bottom of the jar for about 30 seconds. Do not move the blender!
When the liquid at the bottom of the jar starts to look white, opaque and mayo-like, slowly raise the blender through the rest of the oil. The mixture will continue to thicken up as you pull the blender up.
Once you have reached the top and all the oil has been blended in, turn off the blender and you’re done! Season more to taste, if desired, and store in the fridge in the jar you used to blend it.
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Notes
Feel free to experiment with the mustards, vinegars, and oils you use in your mayo until you find the perfect combo for your family. This is our favorite as it most closely resembles the avocado oil mayos that you get from the grocery store.