Step 1 Place the yolks, vinegar, 1 tablespoon water, salt and pepper in a 2-cup measuring cup or a tall beaker used for immersion blenders. Stand the immersion blender in the beaker or measuring cup, then slowly pour in the canola oil so that it settles on top of the other ingredients. (If you've heated the yolks first, allow them, along with the vinegar, salt and pepper, to settle for about 5 minutes after adding the oil so that the oil rises to the top.)
Step 2 With the blender held against the bottom of the glass, pulse until the mixture begins to emulsify, almost immediately. Continue to pulse, turning the blender a bit, but keeping it pressed against the bottom of the container. Keep pulsing until most of the mayonnaise is emulsified, less than 1 minute, then slowly plunge the blender a bit to mix thoroughly. Spoon the mayonnaise into a medium bowl, then whisk in the olive oil and lemon juice until very well combined. Serve immediately or store tightly covered in the refrigerator for up to 2 days.
Step 3To make using a food processor:
Step 4In the bowl of a food processor, pulse the yolks, vinegar, 1 tablespoon water, salt and pepper until well combined.
Step 5Add the canola oil in a very, very slow stream until the mayonnaise thickens and all of the oil is incorporated. Spoon the mayonnaise into a medium bowl and whisk in the olive oil and lemon juice until very well combined. Serve immediately or store tightly covered in the refrigerator for up to 2 days.