• Preheat the oven to 425ºF (220ºC).

Roast the potatoes:

• Cut the potatoes into ½-inch (12 mm) imperfect chunks. Pile them in the center of a baking sheet, drizzle with 2 tablespoons oil, and sprinkle with the chili powder and salt. Toss the potatoes to coat evenly, spread in a single layer, and roast for about 18 minutes, stirring once halfway through, until browned and tender. It's ok to get these in the oven before it's fully preheated.

Sear the corn and heat the beans:

• Preheat a large skillet over medium-high heat, add the frozen corn kernels, and cook, stirring occasionally, until they develop a nice sear and lightly charred spots, about 7 minutes. Mince the garlic and add it to the pan along with the cumin and salt. Cook for a minute.
• Drain and rinse the black beans and add them to the skillet. Cook for a few minutes, stirring occasionally, until the beans are heated through.

Make the guacamole and prepare garnishes:

• Finely mince the onion and chop the cilantro. Cut the avocados in half and remove the pits. Scoop the flesh into a bowl and mash with a fork. Stir in the lime juice, salt, black pepper, onion, and cilantro. Taste and adjust the seasoning if needed.
• Thinly slice a few radishes and scallions to garnish. Cut lime wedges.

Assemble:

• Warm the tortillas in a dry skillet over medium heat, about 30 seconds per side (or use your favorite method, options above). Place some guac in the center of each. Add the beans and corn, then the potatoes. Garnish with radishes, scallion and serve with lime wedges and hot sauce.