Heat the oven to 375 degrees F. In a bowl, combine the Baking Mix with the zest and the blueberries. Break the egg into the buttermilk and stir with a fork; add the sugar and stir briefly to combine. Make a shallow well in the dry mix and pour in the wet ingredients. With as few strokes as possible, stir until the mixture is just combined. It should be loose, but if it doesn't hold together at all, add more buttermilk 1 tablespoon at a time.

Generously flour a counter and turn the dough out onto it; it will be shaggy and very soft. Scrape any bits in the bowl onto the mound of dough. Flour your hands. Shape the mixture into a very loose rectangle with the short side nearest you. Using a bench knife, a pastry scraper, or a spatula to help lift the ragged dough, fold the bottom third over the center third, and then the top third over the center, as if you're folding a business letter. Pat down to shape another rectangle, turn it so the short side is nearest you, and repeat the folding. Divide the dough and shape each half into a round about 3/4 inch thick. With a pastry brush, brush off the excess flour. With a sharp knife, cut the rounds into six wedges each. Brush the tops with buttermilk and sprinkle them with-sugar. Bake on an ungreased baking sheet (or one lined with parchment) until golden brown, 25 to 30 minutes.

Variations: In place of the blueberries, try 1/2 cup dried fruit, like currants or apricots, chopped if large, or 1 cup of your favorite berries or nuts. You could also replace the lemon zest with orange.

In a large bowl, stir the flour, sugar, baking powder, baking soda, and salt. Cut or massage the butter into the flour with a fork, a pastry cutter, or your fingers until the mixture looks like cornmeal and the biggest pieces of butter are the size of large peas. (You can also do this in a food processor; just be sure not to overmix.) Proceed with Herbed Cheese Buttermilk Biscuits, Blueberry Scones, Shortcake Biscuits, or Fruit Cobbler, or refrigerate or freeze the mixture until ready to use.