1. Whisk together flour, ¼ cup sugar, baking powder, and ½ tsp. salt in a
large bowl; add butter, and using your fingers, rub butter into flour until
pea-size crumbles form. Add milk, and stir just until a moist dough forms; cover
and refrigerate dough until ready to use.
2. Heat oven to 400°. Bring remaining sugar and salt along with blueberries and
citrus juices to a boil in a 12″ cast-iron or enamelware skillet over high heat,
stirring to dissolve sugar. Remove pan from heat, and using two tablespoons,
portion and form chilled dough into 2–3″ oval dumplings, and drop them evenly on
top of the blueberry mixture. Sprinkle dough dumplings with sugar, and transfer
skillet to oven; bake until biscuits are cooked through and blueberry mixture is
reduced, about 25 minutes. Serve hot with vanilla ice cream, if you like.