Cornstarch is really meant to thicken gravies and other liquids where the raw flavor can be cooked away and the texture is blended in. Using it in mayonnaise or any other uncooked food would likely be unpleasant and would not give you the result you're looking for. A good mayonnaise is already pretty thick.
For one egg yolk, typically 8oz. of oil is used for consistency or regular mayonaise when making from scratch. Try using one and a half yolks and squeezing a little lemon juice to help thicken.
no NEVER cornstarch, it will make it taste chalky and gritty, rather use more egg yolk, uncooked of course, and whipped into your existing mixture and store below 40 degrees F to inhibit bacterial growth.
No. Cornstarch will not work. I believe that the only way you can make thicker mayonnaise is if you make the product from scratch and increase the amount of egg yolks in the recipe.
