Breaking the butter into pea-sized pieces into the flour creates a light and flaky soft crumb. The fat coats the proteins in the flour, which limits the formation of the protein bonds. Mix the ingredients only until just combined, then chill the dough before rolling. This allows the butter to solidify and for the gluten to relax so, it's easier to handle. Roll and cut the dough only once. The less you handle the dough, the more tender the shortcake!