"Mayonnaise is an emulsion of oil and water—two liquids that generally don't get along. Classic technique will have you start by whisking egg yolks, a bit of mustard (for flavor and its emulsifying properties), a few drops of water, and some acid (either lemon juice or vinegar), then slowly slowly slowly trickling in a thin stream of oil as you continue to beat rapidly. The idea is to get the oil to disperse itself into tiny droplets as you whisk it. Pour the oil too fast, and you end up not with a smooth, rich, creamy sauce, but with a broken, greasy, curdled-looking mess. About half the time I try and make mayonnaise with this method, it breaks and I'm forced to start the process over again. The easy solution? Use a hand blender. With a hand blender you can add all of your ingredients—oil included—directly to the blending cup. Because it is less dense than the other ingredients, the oil will float at the top. When you subsequently stick the blades of the hand blender down into the cup, they'll be in direct contact with the egg yolk, water, acid, and mustard. Turn that blender on, and it creates a vortex, gradually pulling the oil down into the whirling blades. In no time flat, you end up with a cup full of creamy, perfectly emulsified, real-deal, better-than-anything-you-can-buy mayonnaise...."