Process 1 pasteurized large egg, 2 teaspoons lemon juice, 1 teaspoon Dijon mustard, and ½ teaspoon kosher salt together in a food processor until combined, about 15 seconds. Stop and scrape down the sides of the bowl with a flexible spatula.

Measure out 1 cup neutral oil in a liquid measuring cup or container with a spout. With the food processor running, start adding the oil through the feed tube a drop or two at a time until about ¼ cup has been added in and the mixture starts to thicken. Continue pouring in the remaining oil in a thin, steady stream, and process until thick and creamy. If there is any unincorporated oil pooling near the blades, scrape down the sides of the bowl and process again until incorporated.

Place 1 pasteurized large egg, 2 teaspoons lemon juice, 1 teaspoon Dijon mustard, and ½ teaspoon kosher salt in a tall jar (like a 3-cup Mason jar) or transparent container that is just a bit wider than the head of the immersion blender. (If you don’t have one, it’s best to use one of the other options for making mayonnaise.) Pour 1 cup neutral oil on top.

Insert the immersion blender, making sure it is sitting against the bottom of the jar. Turn the blender on (use the low setting if available) but do not move or lift it. Blend until the bottom starts to look more mayonnaise-like, then slowly lift and tilt the blender up to blend in all the oil until thick and creamy.