Directions:

Place the egg, dry mustard, salt and lemon juice in the blender. Add 1/4 cup of the oil and whirl until well mixed - about 20-30 seconds.

Most Important Part!! - Remaining job is to incorporate remaining 1 cup oil into the mixture. To do this, you must pour very slowly ... the skinniest drizzle you can manage and still have movement in the oil. It takes about 3 minutes or so; drizzle slowly. If using a blender, you'll hear the pitch change as liquid starts to form the emulsion.

Eventually the substance in the blender starts to look like regular mayonnaise. Do not lose nerve and consider dumping; just continue to drizzle until all the olive oil is in the mixture and the mayo is light and fluffy.

If something goes wrong, the emulsion will "break" and it will have the consistency of, say, commercial salad dressing. It can be saved! Pour the liquid into a storage container and place in coldest part of fridge. Wait a few hours, stir vigorously; it will be slightly less thick and creamy than the full emulsion, but delicious and useful for salads - egg salad, tuna salad, cucumber salad. It just won't be spreadable.