Pull out the soft center of the baguette and pull into small pieces. Reserve the crust for another use. In a saute pan, melt 2 tablespoons of the butter over medium heat. When the butter is very hot, add the breadcrumbs and cook, stirring constantly, until dark golden brown and crunchy, 7 to 10 minutes. Stir in the paprika and salt to taste. Transfer the breadcrumbs to a paper towel-lined plate. Set aside.
In a heavy-bottomed 12-inch skillet, melt the remaining 2 tablespoons of butter over medium heat. Add the cabbage, rosemary and 1/4 teaspoon salt. Cook, stirring occasionally, until the cabbage starts to wilt, about 5 minutes. Add the hard cider, stir, cover and cook until the liquid evaporates, 12 to 15 minutes. Remove the lid and add 2 tablespoons apple cider vinegar. Stir constantly until the cabbage is completely tender, about 3 minutes. Season to taste, adding more apple cider vinegar if desired, and top with the sauteed breadcrumbs. Serve immediately.