Ingredients

• 1 egg
• ¹⁄₂ a lemon (or ~1 tbsp lemon juice)
• 1 tsp dijon mustard
• ³⁄₄ tsp kosher salt
• 1 cup olive or canola oil

Method

• Get a mason jar and a stick blender
• Make sure the jar is just bigger than the diameter of the blender
• Add all the ingredients in order (egg needs to be on the bottom, oil on top)
• Put the stick blender in the jar and hold it tightly to the bottom
• Turn on high speed, do not pulse or move the head
• As it starts incorporating, slowly lift and tilt the blender around a bit until all the oil is emulsified
• Taste and adjust seasoning

Notes

This is the Serious Eats method, see also the Food Wishes method (which can use up excess yolks).