I wouldn’t be Peruvian if I didn’t love causas, the Peruvian equivalent of a chilled potato casserole with various toppings.
Traditionally, even individual causas are usually pretty big, lasagna-size servings. You eat one, and you are full. Some of the toppings can also get pretty basic. I wanted fresher, lighter, and more unexpected flavors, so I came up with these small, bite-size causas that are more in line with sushi so people can taste several. As the chef, you can play around with different toppings. Use cookie cutters to make large molded causas or smaller bite-size shapes. (My daughter can cut out little pink potato hearts and stars with the beet causa base for what seems like all afternoon.) If you’re short on time, there’s always the old-school option: a Peruvian casserole. Once, I took a classic, casserole-style causa to a fancy chef’s picnic, and everyone wanted to know about the “elegant” dish. My mom would have gotten a kick out of that.
You can top a casserole-style causa the day before you plan to serve it; just cover it well and keep it in the refrigerator (don’t add vegetables that don’t refrigerate well, like tomatoes, until just before serving). If you are making smaller, individual causas, it’s best to top them within an hour or two of serving so the potato base doesn’t dry out.
Lightly rub the bottom and sides of a 9 x 13-inch casserole dish with olive oil. With your hands, press the potatoes evenly into the dish and smooth the top with your hands or an offset spatula (with a casserole, it doesn’t need to be perfectly smooth). Add whatever toppings you’d like, cover, and refrigerate for at least 6 hours or overnight. If you are using toppings like avocados that discolor or fresh seafood fillings, wait to add the toppings until serving the causa. Cut the casserole into generous squares and use a spatula to remove each causa (the first one can be tricky to remove—consider it a snack). Serves 8 to 10 as a light main dish.
Lightly rub the bottom and sides of a large rimmed baking sheet with olive oil. With your hands, press the potatoes into the pan, starting at one edge, so you have a 10 x 12 inch rectangle about ¾ inch thick. The potatoes shouldn't reach all the way to the opposite side. Use an offset spatula to make a straight edge on the “open” end of the potatoes, then smooth the top as much as possible so they look nice when you add the toppings. Cover the baking sheet and refrigerate the causa base for at least 6 hours or up to 2 days. Slice the potatoes into 2 x 1-inch rectangles, or whatever size you’d like. To make panko-crusted causas (which need to be small to fry properly), cut the causas into 2 x 1-inch rectangles or use small cookie cutters to cut different-size rectangles and cutouts in each pan. To remove the causa base, start at the end of the rectangle that is not touching the edges of the pan and use an offset spatula to transfer the rectangles to a serving plate or work surface. Top each causa as you like. The yield varies, but count on around 5 dozen 2 x 1-inch sushi-style causas or 3 to 4 dozen cut-out causas.
Cover and refrigerate the causa base in a bowl for at least 6 hours or up to 2 days. Rub the inside of a ring mold very lightly with olive oil and place it on a serving plate. I use a 3-inch ring mold for a main-dish serving and smaller ring molds for appetizers. Use your fingers to press the causa base into the bottom of the mold so the potatoes come ¾ to 1 inch up the sides of the mold. Press down and smooth the top of the potatoes with your fingers or the back of a small spoon, spread the toppings all the way to the edges of the mold, and smooth them out nicely. Remove the ring mold. Swipe the inside with a few drops of olive oil before making more causas. Serves about 18 as a light main course or side dish (using 3-inch ring molds), or more if you are making smaller causas.