Preheat the oven to 400 degrees F.

Toss the sweet potatoes with 1 tablespoon olive oil and arrange in an even layer on a parchment-lined baking sheet. Roast in the oven until tender and caramelized, 20 minutes. Set aside.

Meanwhile, heat 1 tablespoon of oil in a large cast iron or nonstick skillet. Cook the burgers over medium heat until defrosted and firm, about 7 minutes. Carefully flip and cook for another 5 minutes, until browned and crisp. Set aside until cool enough to touch, then roughly chop.

Add another drizzle of oil to the pan and cook the tortillas in batches, flipping a few times, until golden and stiff, about 3 minutes. Remove to a plate.

Add the leeks, white scallions, and kale to the pan. Cook over medium heat, stirring occasionally, until soft, about 5 minutes. Stir in the garlic, cumin and chili powder. Cook another minute, until fragrant. Add the tomatoes and season with ½ teaspoon salt. Sauté until the tomatoes have softened and released their juices, 5 minutes. Stir in the roasted sweet potatoes and remove from the heat.

Arrange half of the tortillas in the bottom of a 9-inch pie plate or casserole. Top with half of the kale mixture, half the bean burgers, and then half of the cheese. Repeat with the remaining tortillas, kale, burgers and cheese. Cover with foil and bake until melted and gooey, about 10 minutes.

Garnish with green scallions and serve immediately.