If you don't have an immersion blender, move along.

Ingredients

• 1 whole egg
• 1 generous tsp of strong Dijon mustard
• 25 cl of sunflower oil
• salt, pepper

Use a glass jar like a Bonne Maman jam jar, and make sure your immersion blender fits inside it... the idea is that the blender just fits in the jar. Place the egg, mustard, salt, and pepper in the jar. Position your blender, and add 10 cl of oil. Blend while gently lifting the blender and add the remaining oil in 3 or 4 additions. Add a drizzle of white vinegar or lemon juice, and store in the refrigerator in that same jar.