Heat the oven to 425F. Halve the sweet potatoes lengthwise, rub the cut faces with oil, and roast cut side down on a lined sheet pan for 35 minutes, until collapsing and caramelized against the pan.

Let them cool, then scoop the flesh out and discard the skins. You should have about 1 ½ cups.

Drain and rinse the chickpeas, spread them on a clean towel and pat dry. Mash them in a large bowl with a fork or potato masher, leaving about a third in recognizable halves. Do not puree them.

Add the scooped sweet potato, egg, panko, chickpea flour, red onion, garlic, cumin, smoked paprika, salt, pepper, lemon juice and parsley to the chickpeas. Fold together until evenly combined. If the mix is genuinely wet, add 2 more tablespoons of panko.

Cover and refrigerate 30 minutes. Do not skip this step, it is what lets the patties hold their edges.

Divide into 6 portions of about ½ cup each and press each one into a thick round patty roughly 3 ½ inches across and ¾ inch thick. Pinch any cracks at the edges closed.

Heat the olive oil in a skillet over medium-high heat and cook three patties at a time for 4 to 5 minutes per side. Do not move them for the first four minutes or the crust will not form.

To bake instead, arrange them on an oiled sheet pan and bake at 400F for 25 minutes, flipping once halfway through.

Stir the yogurt, lemon juice and grated garlic together with a pinch of salt. Serve each patty on a toasted bun with the yogurt sauce, lettuce and pickled red onion.