Eggnog Cupcakes with Spiced Rum

self-rising flour1 1/4 cups all-purpose flour1 cup (2 sticks) unsalted butter, softened2 cups sugar4 large eggs, at room temperature¾ cup eggnog¼ cup milk1 teaspoon vanilla extract

large egg whites11/2 cup sugar4 sticks unsalted butter, diced and softened1/4 teaspoon salt½ cup spiced rum