Preheat the oven to 350 degrees Fahrenheit.
Add the blackberries to a large bowl, and toss them with 1/4 cup of the granulated sugar. Set them aside. 2 1/2 cups Fresh Blackberries, 6 TBS Granulated Sugar
Melt the butter in a small microwave safe bowl. Use a silicone basting brush to spread a little of the butter over the sides and bottom of a 9x9 inch dish (or other similar size dish). Set the rest of the butter aside. 1/2 cup Unsalted Butter
Add the sugar, flour, baking powder, and salt to a medium bowl and whisk them together. Stir in the milk and vanilla extract. 1 cup Granulated Sugar, 1 cup All Purpose Flour, 1 1/2 tsp Baking Powder, 1/2 tsp Salt, 1 cup Whole Milk, 1 cup Vanilla Extract
Add in the butter and stir together until you have a nice cake batter.
Pour the batter into the buttered baking dish.
Sprinkle 2 cups of the sugared blackberries evenly over the top of the batter, spreading them evenly. Sprinkle the top with 1 more TBS of sugar.
Bake in the oven for 50-60 minutes, or until the crust is golden and cooked and the berries are bubbly. Add the remaining 1/2 cup of blackberries on top of the cake the last 10-20 minutes of baking, if desired so you have some on the top of the cake for looks. Sprinkle the final 1 TBS of sugar on top of the cake as well, the last 10 minutes of baking.
Remove from the oven and let the cobbler cool for 10 minutes, then serve warm with whipped cream or vanilla ice cream on top.