Melt butter in a large nonstick skillet over medium-high heat. Add apple, shallots, celery, and garlic; sauté 5 minutes or until lightly browned. Stir in flour and curry powder; cook 1 minute, stirring frequently. Gradually add the milk, raisins, and broth, stirring constantly with a whisk; bring to a boil, stirring frequently. Reduce heat, and simmer until thick (about 5 minutes). Stir in the shrimp, salt, and pepper; cook 3 minutes or until shrimp are done.