Making homemade mayonnaise does not require an immersion blender...but it is a whole lot easier if you do. Hand-whisking is traditional and takes a bit of finesse. However, the immersion method takes less than a minute and works like magic.
Once you taste homemade mayo, you will be spoiled against any of the store-bought brands. Try this on your next sandwich. Heavy on the mayo please.
Easy Homemade Mayonnaise
Working with a tall, slender container that will hold at least 2 cups, add in order, 1 1/2 tablespoons white wine vinegar, 1 tablespoon Dijon mustard, 1/2 teaspoon kosher salt, 1 egg, and then 2 cups of canola oil. I use a blend of canola (1 3/4 cups) and olive oil (1/4 cup).
Lower the immersion blender into the container so that it sits at the bottom. Puree for 5 seconds, then slowly pull the blender up swirling and incorporating the oil until emulsified, roughly 25 seconds.
Store the mayonnaise in a glass jar with a tight lid. The mayo keeps in the refrigerator for several weeks.