How to make a marvellously smooth mayonnaise

What you need

1 egg yolk

1 tbsp lemon juice

1 tsp Dijon mustard 250 ml vegetable oil

OIL and water famously don’t play well together. Water is a polar molecule, with a negative charge concentrated around the oxygen atom and a positive charge at the two hydrogen atoms. This means that water molecules attract each other, the hydrogen atoms forming bonds with the oxygen atoms of nearby molecules. Oil, on the other hand, is made from non-polar molecules, which aren’t attracted by the water molecules, so it is hard for them to mingle.

If you shake oil and…