Ingredients

• Large wire whisk or electric blender
• 3 egg yolks
• 1 tablespoon wine vinegar or lemon juice (more drops as needed to taste)
• 1/2 teaspoon salt
• 1/4 teaspoon dry or prepared mustard
• 1-1/2 to 2 cups of olive oil or macadamia oil- or a mixture of each. 
• If the oil is cold, heat it to tepid; and if you are a novice, use the minimum amount.
• 2 tablespoons boiling water

Method

Make sure all ingredients are at room temperature.  I just sit everything on the kitchen bench for a couple of hours prior.
Beat egg yolks for a minute or two before adding the oil, they need to get thick, sticky and glossy first.
Add the oil very slowly, a droplet at a time, until the emulsion process begins and the mix turns into a heavy cream, after which you can pour the rest of the oil much quicker.
The maximum amount of oil one egg yolk can absorb is about 3/4 cups- after which the binding properties of the egg break down and the sauce starts to thin and curdle. 
The safest amount is 1/2 cup of oil per egg yolk so stick to that when starting out. 
The proportions of ingredients look something like this: 2 egg yolks+1 cup fat (oil) + 2-3 tablespoons vinegar/lemon juice= about 1 1/2 cups mayonnaise. Then you can also add mustard, garlic powder, anchovies, capers, dill and so on.
The directions are for a hand-beaten sauce (using a wire whisk). For electric beaters, use the large bowl and the speed that you would for whipping cream. 
Use a round-bottomed glass or stainless steel mixing bowl. Set it on a damp towel to keep it from slipping.