Bring balsamic vinegar to a boil in a small saucepan. Reduce about 25 minutes or until thickened. Set aside.
Place puff pastry sheet on a lightly floured surface; sprinkle with Parmesan.
Wrap one heart of palm with a slice of prosciutto; place on the edge of puff pastry. Repeat procedure with another heart of palm and prosciutto slice, lining them up along the bottom edge of puff pastry.
Roll puff pastry once around prosciutto-wrapped hearts of palm. Slice pastry about 1/2 inch to 1 inch away from hearts of palm so there is enough pastry to seal closed.
Place roll, seam-side down, on a foil-lined baking sheet. Repeat procedure with remaining hearts of palm, prosciutto, and pastry. (The diameter of hearts of palm varies, so keep similar sizes together for easier rolling. The number of hearts of palm will vary in the can; save extra pieces for other purposes.)
Bake at 400 for 12 minutes or until golden brown. Cool slightly, and cut into 1-inch pieces.
Drizzle with balsamic reduction, and dollop with Garlic Rmoulade.
