Making a recipe that calls for shallots? Feel free to substitute white onion for the shallot. Shallots are part of the onion family and have a mild onion-garlic flavor. In place of 3 to 4 shallots, use 1 medium onion plus a pinch of garlic powder or (if you like the taste of garlic) 1 minced garlic clove. For this recipe, use 1/2 small white onion, diced, with a pinch of garlic powder or one small clove of garlic.