Immersion Blender Method:

• Put all ingredients in a small bowl with sloped sides.
  
• Put the immersion blender into the bowl, making sure it reaches all the way to the bottom of the ingredients. Start blending, a bit at a time, pulling the immersion blender slowly up through the mixture toward the top. Do this several times, until mixture really begins to emulsify and look like mayonnaise.
  
• Now you can move the immersion blender more freely around the bowl, blending in any areas where liquids still remain separated.
  

Stand Blender Method:

• Place the egg yolks and lemon juice into the blender and beat on high for about a minute, until color begins to lighten.
• With blender running, start to very, very slowly drizzle in the oil. Continue adding oil and blending until the texture is right - you'll clearly notice a change in sound as the mixture emulsifies and gets close to being the right consistency.
  
• Add ground mustard and salt, then give it another quick blitz to blend them in.
  

Store mayo in a tightly-sealed container in the fridge for up to two weeks.