Note: When choosing to make homemade mayonnaise, there can be a concern over any risk associated with the use of raw eggs. Using pasteurized eggs in recipes calling for raw eggs is a recommended alternative (http://www.foodsafety.gov/keep/types/eggs/index.html). If you’d prefer to use a raw egg, it’s recommended to use fresh, properly refrigerated, clean eggs with intact shells from a trusted source.
To separate the eggs: Crack the egg. Hold the bottom half of the egg in one hand with the egg facing up and remove the top half of the shell. The white part should slowly drain out of the crack and keep the egg yolk in the bottom of the shell that you're holding.
In a large bowl or food processor, whisk egg yolk, mustard, lemon juice and salt until combined. Slowly pour in the olive oil, whisking constantly, until emulsified. Whisk to your desired consistency (the longer you whisk, the thicker your mayonnaise).