Heat the oven to 425°F and line a sheet pan with parchment paper.

Soak the cut potatoes in cold water for 15 minutes, drain, and pat completely dry.

Toss with oil, cornstarch and salt, spread in a single layer, and bake 35 to 40 minutes, flipping once, until deep golden and crisp.

While the fries bake, melt the butter in a dry skillet over medium-high heat and add the corn in a single layer.

Cook the corn 6 to 8 minutes without stirring too often, until it picks up real brown char spots, then remove from heat.

Whisk the mayonnaise, sour cream, lime juice and chili powder together in a small bowl until smooth.

Pile the hot fries onto a platter and drizzle with half the crema mixture.

Scatter the charred corn, cotija and cilantro over the top, then drizzle with the remaining crema and dust with extra chili powder.

Serve with lime wedges on the side for squeezing over just before eating.