A day before you plan to eat them, generously season the wings on both sides with kosher salt, garlic powder, and black pepper. Spread the wings out on a drying rack set inside a rimmed baking sheet. Refrigerate the wings overnight.
Set a grill for a medium indirect heat, about 375º F. Grill the wings directly on the grates until they reach 155 F, roughly 25 minutes. Meanwhile, make the boysenberry sauce.
Combine the boysenberry jam, fresh blackberries, grated fresh ginger, vinegar and a pinch of salt in a medium saucepan over medium heat and cook until the fresh berries burst and it starts to thicken, about 5 minutes. Add the ketchup, molasses, sugar, chili flakes and ground chile powder. Season with more salt and black pepper and cook for an additional 5 minutes, or until thickened.
Remove the wings from the grill to a large bowl and toss with half of the sauce. Set the grill to medium-high heat, about 450 F. Return the wings to the grill over direct heat. Your goal is a good char, about 2 minutes per side. Be careful, these can go from charred to burned quickly.
Serve the wings hot with additional boysenberry sauce for dipping and our Aviation Gin Mule.