1In 2-quart saucepan, beat cold water and cornstarch with whisk until cornstarch is dissolved. Add the 2 1/4 cups blackberries, the sugar, maple syrup and vanilla. Heat to boiling over medium-high heat, stirring frequently and breaking up blackberries with a fork until mashed. Reduce heat; simmer 5 to 10 minutes. Remove from heat; set aside. The mixture will thicken slightly as it cools.
2In medium bowl, place Bisquick mix; add buttermilk, eggs and vanilla. Mix until just combined, being careful not to overmix. Stir in the mashed blackberries. Let stand 5 minutes.
3Heat 10-inch skillet or griddle over medium heat (grease if necessary). Spoon batter into 1/4 cup rounds, and cook until bubbles form on top, 2 to 3 minutes. Turn; cook a minute or two longer. Repeat with remaining batter. Serve hot with blackberry syrup.