In a deep jar (wide enough to fit an immersion blender), add chickpea liquid, garlic, vinegar, salt, and mustard.
Blend for 45 seconds, ensuring that everything is blended up very smooth, slightly thickened, and emulsified. It will still be fairly runny at this point.
To the jar, drizzle in avocado oil – SO SLOW. You don’t want to add more than 1-2 tsp at a time. Stop drizzling and blend for 20 seconds after every 2 tsp.
After 1/4 cup of the oil has been added, begin to add in 1-2 tbsp each time and blend for 20 seconds after each addition.
Repeat step 4 until all of the 1 cup of oil has been added. After 1/2-3/4 cup of oil has been added, you should start to see the consistency of mayo. If you don’t, stop adding the oil and blend until it’s thickened. (I like to stir the immersion blender around while it’s blending. )
Store in an airtight container in the fridge. Keeps for up to 7 days. It’s even better the second day once the garlic has really had a chance to infuse the mayo!