Preheat oven to 375.
If using frozen blackberries, take them out of the freezer and add them to a freezer-safe dish.
Make buttermilk by adding vinegar to cream and letting it sit for 5 minutes.
Melt butter in a saucepan or in the microwave in a microwaveable dish.
In a large bowl, add all the dry ingredients together and whisk.
Add to the bowl the wet ingredients and mix together.
To the blackberries, add the sugar and cornstarch, sprinkling the ingredients over the berries.
Add spoonfuls of cobbler batter over the top and smooth out a bit.
Place the dish in the oven for 35-45 minutes depending on the size of the baking dish, until the blackberries are bubbling and the batter is cooked through and golden brown.
Allow to rest for 10 minutes.
Serve with ice cream, whipped cream, or just a touch of heavy whipping cream. It seriously takes it up a notch.