Preheat the oven to 375°F. Grease an 8" square pan or 2-quart baking dish., To prepare the fruit: Whisk together the sugar, Pie Filling Enhancer, and salt., In a large bowl, combine the peaches and blueberries, then toss with the sugar mixture and lemon juice. Spoon into the prepared pan., To make the biscuits: Whisk together the flour and sugar., Work in the butter until the mixture is crumbly, with some small clumps the size of peas., Add the yogurt and vanilla extract, mixing to make a cohesive dough. If the dough doesn't come together, stir in additional yogurt or milk until it does., Drop the biscuit dough by heaping tablespoonfuls over the fruit in the pan; a tablespoon cookie scoop works well here., Sprinkle with sparkling sugar, if desired., Bake the cobbler until the biscuits are golden brown and the fruit is bubbling, 45 to 55 minutes. Remove it from the oven, and serve warm., Yield: 9 to 12 servings.