Mayonnaise is deliciously simple to make and tastes nothing like the stuff you buy in a jar. All you need to make it is a bowl, a whisk, a squeeze bottle, and a few ingredients. It's really handy to have a soft silicone pad that will keep the bowl from moving while you whisk. Alternatively, form a damp towel into a ring and set the bowl into it.
1 egg yolk
2 teaspoons freshly squeezed lemon juice or to taste
1 teaspoon water (optional but useful)
1 teaspoon fleur de sel
1 teaspoon whole grain mustard (optional)
4 ounces (approximately) extra virgin olive oil (optional)
4 ounces (approximately) canola oil (8 ounces without olive oil)
Whisk together the yolk, lemon juice, and water. Then use the squeeze bottle filled with oil to add just a few drops of oil so that you can begin the emulsion. I find that pouring oil from a can or bottle doesn't work well for me--too much oil comes out to start the emulsion.
Once you have the emulsion well started, you can squeeze the bottle to squirt a stream of oil into the mixture. If it looks a little oily, or starts to break up, stop adding oil until it smooths out. If that doesn't work add a splash more cold water and whisk until it comes back together.
After adding about four ounces of olive oil, add the mustard and salt, then switch to canola oil and continue whisking until you've added about 8 ounces total of oil. You can use all canola oil if you wish, I just prefer the more pungent flavor of olive oil. When you've added as much oil as you dare, taste and adjust the seasoning.
That's it. No real fuss, just a bit of work, and you've got a great tasting cup of mayonnaise. Use it immediately, or refrigerate for a day.
Some people use a food processor to make mayonnaise. For whatever reason, I've never succeeded with a food processor. Since I'm quite happy with the result of doing it by hand, I don't really care.
There are lots of options you can use to extend this mother recipe. Try adding a pinch of chipotle powder or minced chipotles in adobo for a spicy mayo. Some freshly ground wasabi makes a very nice twist on the classic. In fact, almost anything you think might taste good in mayonnaise works just fine. Have fun!