This is roughly the recipe from my Mamaw and the way I make mine every time.
Operating under the constraint of utilizing twelve already hard-boiled eggs requires managing moisture before it compromises the whites. Water is the primary enemy of structure here, meaning every component added to the yolk base must be evaluated for its liquid content. Finely mincing the onions and pickles prevents chunky intrusions that disrupt the smooth emulsion of fat and protein. Freshly ground black pepper provides a sharp visual contrast and volatile aromatics without introducing excess moisture.
Achieving a velvety mouthfeel relies entirely on mechanical action before the fats are introduced. Mash the yolks thoroughly with the melted unsalted butter, minced aromatics, and pepper before incorporating the mayonnaise and mustard. Adding solid fats and seasonings first allows the yolks to break down completely against the bowl without slipping in the lubrication of the liquid condiments. Once a smooth paste forms, fold in the mayonnaise gradually until the mixture achieves a consistency thick enough to hold a peak on a spoon without slumping. Delaying the kosher salt addition until the very end prevents premature moisture extraction from the onions, ensuring the mixture does not water down during assembly.
Resting the assembled eggs in the refrigerator for at least one hour transforms the physical properties of the filling. The butter and mayonnaise firm up as their temperature drops, turning a loose paste into a stable, sliceable mound. Garnish the chilled surface with paprika just before serving to add a subtle phenolic bite that cuts through the rich egg fat.