Step 1

First, cook the beets: Heat the oven to 400°F. Wrap the beets loosely in aluminum foil and roast until easily pierced with a fork, 50 to 60 minutes. Set aside to cool.

Step 2

Cook the rice while the beets roast: Meanwhile, 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.

Step 3

Begin sautéing the onions when you're done with the rice (or during, if you're OK with multitasking!): 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, and cook until they are golden and getting charred around the edges, 10 to 12 minutes. A few wisps of smoke as you are cooking are OK, but if it seems like the onions are burning, lower the heat. A dark, sticky crust should develop on the bottom of the pan.Add the garlic and cook until it is fragrant, about 30 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.

Step 4

Process the oats in a food processor until they have reduced to a fine flour. Transfer to a small bowl and set aside.

Step 5

Drain and rinse one of the cans of beans and transfer the beans to the food processor. Scatter the prunes on top. Pulse in 1-second bursts just until the beans are roughly chopped — not so long that they become mush — 8 to 10 pulses. Transfer this mixture to a large mixing bowl. Drain and rinse the second can of beans and add these whole beans to the mixing bowl as well.

Step 6

Grate the roasted beets: Use the edge of a spoon or a paper towel to scrape the skins off the cooled roasted beets; the skins should slip off easily. Grate the peeled beets on the largest holes of a box grater. Transfer the beet gratings to a strainer set over the sink. Press and squeeze the beet gratings to remove as much liquid as possible from the beets. (You can also do this over a bowl and save the beet juice for another purpose.)

Step 7

Combine the veggie burger mix: Transfer the squeezed beets, cooked rice, and sautéed onions to the bowl with the beans. Sprinkle the olive oil, brown mustard, 2 teaspoons of 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 (if using — it helps hold everything together, but isn't 100% necessary), and mix until you no longer see any dry oatmeal or egg.

Step 8

Refrigerate the burger mix 2 hours, or up to 3 days: Cover the bowl with plastic wrap or transfer the mixture to a refrigerator container, and 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.

Step 9

Shape the burgers: When ready to cook the burgers, first shape them into burgers. Scoop up about a scant cup of the burger mixture and shape it between your palms into a thick patty the size of your hamburger buns. You should end up with 6 large patties.

Step 10

Cook the burgers: 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.Transfer the patties to the pan. Cook as many as will fit without crowding; I normally cook 3 patties at a time in my 10-inch cast iron skillet.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. If you're adding cheese, lay a slice over the burgers in the last minute of cooking.Serve the veggie burgers on soft burger buns or lightly toasted sandwich bread along with some fresh greens.