Combine 1 cup water and broth in a Dutch oven; bring to a boil. Break pasta in half; add to pan. Bring mixture to a boil. Cover, reduce heat, and simmer for 8 minutes. Add shrimp to pan. Cover and simmer for 3 minutes or until shrimp are done; drain.
Melt butter in a large skillet over medium-high heat. Add mushrooms and pepper to pan; sauté 4 minutes or until moisture evaporates. Add flour, seasoning, and salt to pan; sauté 30 seconds. Stir in half-and-half; cook 1 minute or until thick, stirring constantly. Remove from heat. Add pasta mixture and parsley to pan; toss.