You can also easily prepare the lemon aioli in a bowl using a whisk: Mix the egg yolk, lemon juice, salt, and Dijon mustard in the bottom of a bowl and whisk together thoroughly. Slowly drizzle in the oil while whisking aggressively until the ingredients have emulsified. When you first start adding the oil, pour very slowly to give the oil time to incorporate into the mixture before adding more. Taste and adjust for seasoning.