Bring a 2-quart pot of water to a boil. Salt the water generously and add the rice. Reduce the heat to a simmer and cook the rice until it's a little beyond al dente. You want it a little over-cooked, but still firm (not completely mushy). This should take about 35 to 40 minutes. Drain the rice and set it aside to cool.
While rice is cooking, peel and grate beets into a colander in a bowl. Press and squeeze the beet gratings to remove as much liquid as possible from the beets. Grate your zucchini into a separate bowl.
Heat a teaspoon of olive oil in a skillet over medium-high heat. Add the onions and a pinch of salt. Stir the onions every minute or two, adding the zucchini when the onions are soft and starting to brown. Cook until they are golden and getting charred around the edges, 10 to 12 minutes.
Add the garlic and cook about 10 seconds. Pour in the cider vinegar and scrape up the dark sticky crust. Continue to simmer until the cider has evaporated and the pan is nearly dry again. Remove from heat and set aside to cool. Using the same pan, start to sauté the beets in 1 Tbsp of oil, covering to let steam for the first few minutes. Stir every minute or two and remove from heat when soft.
Process the oats in a food processor or blender until they have reduced to a fine flour. Transfer to a small bowl and set aside (if you have oat flour at home you can substitute in and use 1/4 cup).
Pulse 1.5 cup beans and prunes in 1-second bursts just until the beans are roughly chopped — 8 to 10 pulses. Transfer this mixture to a large mixing bowl. Add remaining 1.5 cups whole beans to the mixing bowl as well.
Transfer the beets, cooked rice, and sautéed zucchini & onions to the bowl with the beans. Sprinkle the olive oil, mustard, smoked paprika, cumin, coriander, and thyme over the top of the mixture. Mix all the ingredients until combined. Taste the mixture and add salt, pepper, or any additional spices or flavorings to taste. Finally, add the oatmeal flour and egg and mix until you no longer see any dry oatmeal or egg. (The egg helps hold everything together, but can be omitted to make this recipe vegan friendly).
Refrigerate the burger mixture for at least 2 hours or (ideally) overnight. The mix can also be kept refrigerated for up to three days before cooking.
When ready to cook the burgers, shape them into 6 large patties.
Heat a cast iron skillet over high heat. Add a few tablespoons of vegetable oil to completely coat the bottom of the pan. When you see the oil shimmer and a flick of water evaporates on contact, the pan is ready.
Cook the patties for 2 minutes, then flip them to the other side. You should see a nice crust on the cooked side. If any pieces break off when you flip the burgers, just pat them back into place with the spatula. Cook for another 2 minutes, then cover the pan and reduce the heat to medium-low. Cook for 4 more minutes until the patties are warmed through.
Adaptations: Feel free to substitute squash, sweet potato, or carrots for beets. If adding greens or zucchini, cook with onions. Substitute spices to be Italian or Mediterranean seasoning if preferred and use white beans or garbanzo beans. If your budget allows, consider topping with whipped feta and yogurt mixed together, fresh tomato/onion/lettuce, or other preferred toppings.
Freezing Burgers: Burgers can be frozen raw or cooked. Wrap each burger individually in plastic or between sheets of parchment paper, and freeze. Raw burgers are best if thawed in the fridge overnight before cooking. Cooked burgers can be reheated in the oven, a toaster oven, or the microwave.
Recipe adapted by Kim Werst eatclosertohome.com from thekitchn.com