Pour the oil directly into a quart-sized, wide mouth canning jar to the one-cup mark (no measuring cup to wash). Add remaining ingredients. With the blade portion of the blender sitting at the bottom of the jar, pulse three or four times. Now hold the power on while moving the blender up and down in the jar. You'll have nice, thick mayo within 30 seconds.
If it's cool at your place, drop the egg into warm water to bring it up to about 80 degrees in temperature. If the egg is too cool (as your home may be during winter months) you'll have a hard time emulsifying this homemade mayonnaise.