How to Make It
Preheat oven to 375°.
Stir together baking mix and milk in medium bowl until just combined; set aside.
Combine sugar, flour, zest, and salt in a large bowl. Rub together with your fingers to evenly disperse oils in the zest. Add blueberries and vanilla; stir to combine. Place blueberry mixture in a 9-inch, cast-iron skillet. Top with 11/2-inch dollops of Bisquick mixture. Bake 50 minutes-1 hour or until bubbly and biscuits are cooked, tenting top with foil after 20-25 minutes (when biscuits are golden brown). Let stand 10 minutes before serving. Serve warm with vanilla ice cream, if desired.