Step 1

Place egg yolk, lemon juice, water and mustard in a narrow, tall container. I used a Weck jar. Pour over olive oil, then let the contents settle for a moment.

Step 2

Using an immersion blender, process until the mayo starts to form. Once you start seeing mayo, gently move the blender up and down. Continue until all oil is emulsified. The texture will be thick.

Step 3

Season to taste with kosher salt and store in the refrigerator for up to several weeks.