Set a large nonstick or cast-iron skillet over medium heat. Line a plate or small sheet pan with paper towels and set it near the stove.

Mix the cool toppings: In a medium bowl, stir the sour cream with 1 tablespoon of the lime juice and a pinch of salt until smooth. Set it aside for serving.

Put the cabbage in another bowl. Add 1 tablespoon of the neutral oil, the remaining lime juice, and a good pinch of salt, then toss until the cabbage looks glossy and starts to soften.

Set the lime wedges aside for serving at the table.

Build the fritter mixture: Put the drained black beans in a large bowl. Mash about half of them with a fork so you have a mix of mashed beans and whole beans.

Add the grated sweet potato to the bowl with the beans.

Add the scallion whites and about half of the scallion greens to the bowl, saving the rest of the greens for the final topping.

Crack the eggs into a small bowl and beat them with a fork until the yolks and whites are fully mixed.

Pour the beaten eggs into the large bowl. Add the cheddar, flour, and chili powder, then stir until the mixture is evenly combined and holds together when you press some in your hand.

Cook the fritters: Add 2 tablespoons of the neutral oil to the hot skillet. When the oil looks shiny, scoop the fritter mixture into the skillet in 1/4-cup mounds and flatten each one into a patty about 1/2 inch thick. Cook 4 fritters at a time so they are not crowded.

Cook the fritters on the first side for 3 to 4 minutes. They should look deep golden around the edges and release from the skillet when you slide a thin spatula under them.

Flip the fritters in the skillet. Cook the second side for 3 to 4 minutes, until both sides are browned and the centers feel firm, then transfer them to the lined plate.