To make marinade, in a medium bowl blend lemon juice, salt and Worcestershire sauce. Stir until salt is dissolved. Blend in garlic, rosemary, paprika and black pepper. When uniform, gradually stir in a few spoonsful of sour cream, blend again, then stir in all the sour cream.
Rinse chicken breasts and place them in a non-reactive container or self-sealing plastic bag. Pour marinade over and mix by hand to cover each well. Refrigerate for 8 hours. Halfway through marinating, turn breasts over and redistribute the liquid. Remove from refrigerator half an hour before baking.
Preheat oven to 350 F (180 C). Mix bread crumbs and parmesan on a pie plate. Remove chicken breasts from marinade and let the excess liquid drip off. Dip each breast into the bread crumb-parmesan mixture to coat uniformly. Shake off excess crumbs. Place breasts side by side on a lightly oiled baking sheet. Drizzle half of the melted butter over the top. Place the baking sheet in the center of the preheated oven and bake 45 minutes, checking occasionally.
Turn each breast over on the baking sheet and drizzle tops with the rest of the melted butter. Bake 10 more minutes or until nice and brown.
Serve fresh out of the oven garnished with lemon wedges and rosemary sprigs. Parsleyed mashed potatoes or pasta drizzled with olive oil go well with this chicken.