Stir together 1/4 cup lardo, prosciutto, rosemary, garlic and black pepper in a mixing bowl until smooth and set aside.
To cook borlenghe, heat a 14- to 16-inch non-stick pan over medium heat and brush with a 1/4 teaspoon of remaining lardo. Pour enough batter to coat pan (just like a crespella) and return to heat. Cook 4 minutes on the first side and turn carefully. (The texture will not be like a crespella, or anything else, for this is an original and distinct delicacy. It may crack, but keep going). Continue until all the batter is finished, or about 10 to 12 borlenghe.