Heat the olive oil in a large skillet over medium-high heat. Add the venison cubes and cook until browned, about 8 minutes. Remove the venison from the skillet and set aside.
Add the onion and garlic to the skillet and sauté until the onion is softened, about 5 minutes. Pour in the blackberry wine and balsamic vinegar and bring to a boil.
Stir in the brown sugar, rosemary, thyme, black pepper, cumin, and cayenne pepper. Return the venison to the skillet and reduce the heat to low. Simmer for 25 minutes, stirring occasionally.
Add the blackberries and simmer for 10 minutes, stirring occasionally. In a small bowl, whisk together the cornstarch and cold water. Pour into the skillet and stir until the sauce thickens, about 2 minutes.
Remove the skillet from the heat and serve the venison with blackberry wine sauce.
Interesting Facts
Venison is the meat of a deer, usually hunted in the wild.
The blackberry wine sauce adds a sweet and tart flavor to the dish.
The cayenne pepper gives the dish a subtle, spicy kick.