Pound the salt and garlic in a mortar with a pestle into a paste. Transfer to a food processor and add the egg, egg yolk, wasabi powder, and lemon juice. Process for 1 to 2 minutes, or until thoroughly mixed.
Combine the vegetable and olive oils. With the food processor running, slowly add the oil in a thin steady stream, processing until the mayonnaise thickens. Scrape down the sides of the bowl and process until thoroughly blended. Transfer to a glass jar with a lid and refrigerate. The mayonnaise is best within a few hours after it's made, but it will keep in the refrigerator for a couple of days