Butter a 10-inch skillet or round cake pan. Set aside.
For the dough:
Add flour, salt, sugar, shortening, and cold butter to a medium bowl. Cut together with a pastry blender or two forks until the flour mixture resembles coarse crumbs.
Add half-and-half and vinegar to the dough and gently mix together.
Pour onto a floured surface and knead together two or three times until the dough holds together well. Gently press into a rectangle about 1/2-inch thick.
For the filling:
Spread jam onto dough with the back of a spoon. Top with fresh blackberries.
For rolling:
Begin with one long edge of the dough and gently roll the dough so the jam and fruit are in the center.
Cut into 2-inch slices and place into the buttered skillet.
For the topping:
Spoon melted butter over the rolls and then sprinkle with sugar.
For baking:
Bake rolls for 10-12 minutes, or until lightly browned and cooked through. Do not overbake.