Prepare a 9 x 13" baking dish with non-stick coating.
Using large sauté pan, heat 2 tablespoons olive oil over medium high heat.
Cook chicken breasts in pan for about 6 minutes on each side, until internal temperature reads 165 degrees F. Remove from pan, allow to cool, then shred with fork and set aside.
Add 2 tablespoons olive oil to pan, over medium heat and stir in flour.
Gradually add cream and broth until thoroughly combined.
Crumble gorgonzola cheese and add to sauce. Stir until melted.
Add rosemary sprigs.
Bring to boil then reduce heat to low simmer. Cook and stir for about 10 minutes until sauce begins to thicken.
Bring large pot of salted water to boil and prepare shells to al dente, drain and set aside.
In small bowl, combine breadcrumbs, Parmesan cheese, fresh parsley, lemon zest and remaining olive oil. Stir to mix well.
Using large mixing bowl, combine cooked shells with sauce. Add shredded chicken and stir together until completely blended.
Transfer mixture to prepared baking pan. Evenly sprinkle breadcrumb topping over top of shells.
Bake in oven for 25 minutes or until golden brown on top.