01 - Preheat the oven to 375°F. Lightly grease a 9-inch round or square baking dish with butter or nonstick spray.
02 - In a large bowl, gently toss the mixed berries with granulated sugar, cornstarch, lemon juice, vanilla extract, and a pinch of salt until evenly coated. Transfer the mixture to the prepared baking dish and spread into an even layer.
03 - In a separate bowl, whisk together the all-purpose flour, almond flour, sugar, baking powder, and salt until well combined.
04 - Add the cold cubed butter to the flour mixture. Using your fingertips or a pastry cutter, work the butter into the dry ingredients until the mixture resembles coarse crumbs with some pea-sized pieces remaining.
05 - Pour in the milk, vanilla extract, and almond extract. Stir gently with a fork or spatula until just combined. Avoid overmixing to keep the topping tender and flaky.
06 - Drop spoonfuls of the biscuit dough unevenly over the berry filling, leaving gaps between mounds to allow steam to escape during baking.
07 - Scatter sliced almonds and coarse sugar over the biscuit dough for a golden, crunchy finish.
08 - Bake on the center rack for 35 to 40 minutes, or until the biscuit topping is deeply golden and the berry filling is bubbling around the edges.
09 - Allow the cobbler to cool for at least 15 minutes before serving. Serve warm, optionally accompanied by vanilla ice cream or lightly sweetened whipped cream.