Mix the egg yolk, Dijon mustard and balsamic vinegar in a bowl using an immersion blender.
While blending, slowly add the walnut oil.
(Drop by drop to start with, then after a while carefully increasing the amount until you add the last oil in a slow but steady stream.)
Add the truffle oil until the mayo has the taste you prefer.
(It’s quite powerful, and a little goes a long way, so I suggest you add no more than 1/4 tsp at a time and taste it after each…)
NOTE: If you have questions or comments you wish me to respond to, please post them at the original post at the blog: http://strictlypaleoish.com/2013/06/09/truffle-mayonnaise/