1. Peel the potatoes and cut into 3/4-inch pieces. Pour 3 cups of water into the bowl. Place the potatoes in the steam basket and place the basket in the Prep&Cook bowl. Launch the P2 steam program for 30 minutes. At the end of the program, rinse and drain the potatoes. Empty water from the bowl and attach the kneading/crushing blade.
2. Thinly slice the onions. Place potatoes, onions, parsley, peas, tuna, egg, salt and pepper in the bowl. Mix at speed 6 for 15 seconds.
3. Using wet hands, shape about 2 1/2 Tbsp. of mixture into a patty. Repeat until all the mixture is used. Carefully sprinkle or gently roll patties in breadcrumbs. Cover and let croquettes rest for 30 minutes.
4. Over medium-high heat, place 2-3 Tbsp. oil in a 9-inch nonstick skillet. When oil is hot, place a few patties in skillet. Cook for 2 minutes on first side, turn and continue cooking for another 2 minutes or until light brown. Repeat with remaining patties, adding oil if necessary.