Easy homemade mayo. Cheaper than storebought 'natural' mayo by a long shot. The optional whey left over from yogurt making preserves the mayo. Mayo made with whey will keep for 2-3 months in the fridge.
Measure the oil into a cup with a spout.
Blend the first 5 ingredients (everything except the oil) in a straight sided jar using an immersion blender for 30 seconds. With the blender still running, very slowly drizzle in the oil until the mayo is thick and smooth. It's important to drizzle the oil in a very fine stream, otherwise the mixture will not emulsify.
If you included the whey, cover the mayonnaise after blending and let it sit at room temperature for 8 hours before refrigerating. This activates the enzymes in the whey.
If you didn't use whey, refrigerate immediately.
Recipe doubles easily as long as the blending jar is big enough! Alternatively, use a food processor or blender.