From America's Test Kitchen Season 2: Muffins and Scones
British-style scones, or cream scones, are a far cry from humongous American coffeehouse creations. Cream scones are delicate and light, much like a biscuit. We set out to perfect a technique for making these tea-time (or breakfast) favorites.
Experimentation with different kinds of flour revealed that all-purpose is the best choice for scones, and even better, for maximum tenderness, is a lower-protein brand of flour. Butter was important for flavor, but only a modest amount or the scones would practically melt in the oven. Cream won out over buttermilk and whole milk for the liquid; it made our scones rich and kept them tender. As a nod to American taste, we increased the amount of sugar from that used in traditional recipes, but only slightly to keep them from being too sweet. The discovery that the food processor did a great job of cutting the butter into the flour was a boon, making it even easier to make these treats. Our British-style cream scones were just right served with a bit of jam.
The easiest and most reliable approach to mixing the butter into the dry ingredients is to use a food processor fitted with a steel blade. Resist the urge to eat the scones hot out of the oven. Letting them cool for at least 10 minutes firms them up and improves their texture.