Coarsely chop shrimp and sausage in processor, using on/off turns. Melt 1 tablespoon butter in small skillet over medium heat. Add bell pepper and onion; saute until vegetables soften, about 5 minutes. Transfer to medium bowl; cool. Add shrimp and sausage to vegetable mixture. Stir in mayonnaise, 1/2 cup breadcrumbs, green onion, and mustard; season with salt and pepper. Cover and chill 30 minutes. Form shrimp mixture into eight 1-inch-thick cakes. Place remaining 3/4 cup breadcrumbs on plate. Coat each cake with crumbs, patting to adhere. Transfer to plate; cover and chill 15 minutes or up to 1 day. Melt 1 tablespoon butter in heavy large nonstick skillet over medium-low heat. Add shrimp cakes; saute until brown, about 6 minutes per side. Transfer 1 cake to each of 6 plates and serve. Andouille sausage can be found in specialty foods stores and some supermarkets. You can substitute hot links, kielbasa sausage or smoked Hungarian sausage in these recipes.