Egg Yolk Makes Shortbread Shorter: Briony's Secret Technique. When Briony explained she added grated cooked egg yolk to make her biscuits shorter she was using a traditional technique that creates more tender crumbly melt-in-mouth texture. In baking terminology shorter means more delicate and crumbly rather than tough or crisp. Hard-boiled egg yolk contains mostly fat and lecithin which coats flour proteins and limits gluten development during mixing. The lecithin acts as an emulsifier creating exceptionally tender texture. This centuries-old technique transforms standard shortbread into something that melts in the mouth as Prue praised. Hard-boil two eggs let cool completely peel and separate the yolks. Grate on fine grater or mash with fork until crumbly then incorporate into creamed butter and sugar. The result is beautifully crumbly shortbread with superior texture that stays tender longer than standard shortbread.