Step 1Place 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 2With 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.
Variations for flavored mayo:
Chipotle mayonnaise: Add one-fourth cup pureed canned chipotle chiles in adobo to a bowl of basic mayonnaise.
Piquillo pepper mayonnaise: Follow the basic mayonnaise recipe, substituting sherry vinegar for the white wine vinegar. Add one-fourth cup pureed piquillo peppers and a pinch of cayenne to the mayonnaise.
Saffron mayonnaise: Soak a pinch of saffron threads in 1 tablespoon of hot water for 15 minutes, then add the water and threads to the egg-yolk base in place of the plain water. Continue with the recipe for basic mayonnaise.
Tarragon-mustard mayonnaise: Add one-fourth cup finely minced fresh tarragon and one-fourth cup stone-ground mustard to the basic mayonnaise recipe.
Cilantro-lime mayonnaise: Make the basic mayonnaise, replacing the lemon juice with lime juice and adding one-fourth cup finely minced fresh cilantro to the sauce.
Cumin-caraway mayonnaise: Toast 1 tablespoon each of cumin seeds and caraway seeds in a small saucepan, then grind in a spice grinder. Add to the basic mayonnaise.
Garlic mayonnaise (aioli): Using a mortar and pestle, crush 4 garlic cloves with one-fourth teaspoon kosher salt, then add to the egg-yolk mixture. Omit the salt, and continue with the rest of the recipe for basic mayonnaise.
Mustard-caper mayonnaise: To a recipe of basic mayonnaise, add 3 tablespoons Dijon mustard, 2 tablespoons minced capers, 1 mashed anchovy and 1 tablespoon each minced fresh chervil, tarragon and parsley.
Wasabi mayonnaise: To a recipe of basic mayonnaise, add 1 tablespoon fresh or prepared wasabi (Japanese horseradish).