Shuck the corn and wipe off the silk, then stand the cob upright on a cutting board and slice the kernels off with a sharp knife, angling slightly inward to capture the whole kernel.

Heat the larger portion of oil in a wok or pot with a lid over medium-high heat until the oil shimmers. Add the onions and cook, lowering the heat to medium and stirring often, until they are golden brown and charred around the edges, about 8 to 10 minutes.

Use a slotted spoon to transfer the onions to a plate, leaving as much flavored oil in the pan as possible.

Add the remaining oil to the wok and heat over medium-high heat. Add the corn and cook, stirring occasionally, until the kernels begin to char and pop like popcorn—if they start jumping out, use the lid to partially cover the wok.

Stir-fry until the corn is cooked through but not mushy, about 2 minutes. Season with salt and chile flakes, then stir the charred onions back in and serve hot while the corn still has its sweet pop.