When I make aioli I use two olive oils: one is a bit more expensive, a bit more peppery and a bit more gutsy, and the second is a bit more bland but still nice and mellow. By blending the flavors in this way you achieve an olive oil flavor that isn't too strong or too peppery. Aioli is great with cold roast pork. Basil aioli is good with pink grilled salmon, and lemon aioli works well with crostini in fish broth.
Smash up the garlic with the salt in a mortar and pestle (if you don't have a mortar and pestle you can very finely chop the garlic). Place the egg yolk and mustard in a bowl and whisk. Then start to add your olive oil bit by bit. Once you've blended in a half cup of the olive oil you can start to add the rest in larger amounts. When you've added it all, you can add the garlic and lemon (to taste) and any extra flavors such as basil, fennel tops, dill, chopped roast nuts. To finish just season to taste with salt, freshly ground black pepper and lemon juice.
Consumption of raw or undercooked eggs, shellfish and meat may increase the risk of foodborne illness.