In a large skillet cook and stir leeks and garlic in hot butter over medium heat for 3 to 5 minutes or until leek is tender. Stir in rice; cook and stir for 1 minute more. Spoon rice mixture into a 3 1/2- or 4-quart slow cooker. Stir in broth, wine, and pepper.
Cover and cook on high-heat setting for 1 1/4 hours or until rice is tender. Remove crockery liner from cooker, if possible, or turn off cooker. Let risotto stand, uncovered, for 15 minutes before serving.
Transfer risotto to a serving dish/ Top with cheese and Arugula Gremolata. Serve immediately.
From the Test Kitchen
In a small bowl stir together the arugula, prosciutto, pine nuts, lemon peel, and garlic.