Prep: Scrub and halve the potatoes, slice the scallions and jalapeño, chop the cilantro, and crumble the cheese.
Boil the potatoes in salted water for 12–15 minutes until fork-tender, then drain and let them steam out.
While the potatoes cook, place a skillet over medium heat and add the frozen corn straight from the bag.
Cook the corn for 8–9 minutes, stirring every couple of minutes, until cooked through and golden in spots; turn up the heat for the last 2 minutes if you want browning.
In a large bowl, stir together the sour cream, mayo, lime juice, and salt until smooth.
Add the warm potatoes and gently toss to coat them in the dressing.
Add the cooked corn, scallions, jalapeño, and chopped cilantro, and mix again gently.
Top with crumbled cheese and dust with chili powder or smoked paprika.
Serve warm or chilled with lime wedges on the side.