There are veggie burgers, and then there are vegetable burgers. To my mind, the difference is that a veggie burger is made of a carefully concocted blend of beans, grains, various flavorings and a binder, while a vegetable burger is a vegetable on a bun.
In his book "Green Burgers," Swedish cook-author Martin Nordin covers both categories, and his ideas are captivating. This is someone who clearly takes vegetarian burgers seriously, with multicomponent recipes that include inventive sauces, lots of textures and garnishes galore. For one, he deep-fries a mixture of king oyster mushrooms, dried shiitakes and more, then combines them on buns with a kimchi made from zucchini.
I was after something a little simpler, and I couldn't stop returning to his idea of salt-baked sweet potatoes. The salt pulls out enough moisture so when you peel back the skin and scoop out the flesh in one piece, it holds together enough to be eaten between soft hamburger buns.
The other key is a pungent sauce, made from black garlic, vinegar, spices and charred scallion tops. It tastes like the best (vegan) Worcestershire sauce ever. You brush it on the thick patties and top them with a very generous amount of crumbled feta, scallion whites and fresh oregano.
When you take a bite, the first surprise is that the sweet potato doesn't squish out the way so many veggie burgers do. The second is the interplay of flavors. If you're like me, you'll taste, inhale - and start thinking about when to make these again. And again.
Sweet Potato Burgers
Yield: 4 servings
2 scallions 1/2 teaspoon ground coriander 1/2 teaspoon ground Sichuan pepper 1/2 teaspoon freshly ground black pepper 2 tablespoons red wine vinegar 3 black garlic cloves 1/4 teaspoon salt, or more as needed 2 medium sweet potatoes (12 to 16 ounces each; see headnote), scrubbed and dried 4 teaspoons extra-virgin olive oil 2 tablespoons coarse sea salt 4 soft hamburger buns, lightly toasted One 4-ounce block feta cheese, crumbled Leaves from 3 stems fresh oregano, chopped
Position an oven rack 4 to 6 inches from the broiler; preheat to broil. Line a baking sheet with aluminum foil.
Cut the green parts of the scallions, placing them on the baking sheet in a single layer. Broil them until blackened, 8 to 10 minutes, then transfer to a mini food processor or blender. Reduce the oven to 400 degrees. Thinly slice the white parts of the scallions, and reserve them for garnishing the burgers.
Add the coriander, Sichuan pepper, black pepper, vinegar, black garlic and 1/4 teaspoon salt to the burnt scallion tops; puree until smooth. Taste and add salt as needed. You should have about 2 tablespoons of sauce.
Place the sweet potatoes on the same foil-lined baking sheet, rub each with 2 teaspoons of the oil and sprinkle each with 1 tablespoon of the coarse salt. Roast until they are completely soft to a skewer, 45 minutes to 1 hour.
Make a shallow cut (just through the skin) of each sweet potato, and peel off the skins. Use a large spoon to carefully scoop out two halves from each potato, trying to keep the flesh in one piece without mashing. Discard the skins.
Gently shape the sweet potato flesh, being careful to not mash it, into 4 thick, round patties (about 1/2 cup's worth of flesh each). Use a spatula to place a sweet potato patty on each bottom bun. Brush black garlic sauce on each patty, then crumble the feta on each. Top with the sliced scallion whites, oregano and the top buns. Serve warm.
Note: Look for black garlic - fermented to become dark, soft, sticky and a little sweet - in the produce section of Whole Foods and Trader Joe's, among other stores. Sichuan pepper can be found in spice stores, Asian markets and the spice section of particularly well-stocked supermarkets.
Nutrition information per serving: 290 calories, 11 g protein, 45 g carbohydrates, 8 g fat, 5 g saturated fat, 25 mg cholesterol, 660 mg sodium, 5 g dietary fiber, 11 g sugar.
Source: Adapted from "Green Burgers: Creative Vegetarian Recipes for Burgers and Sides," by Martin Nordin.