Brush the corn cobs with vegetable oil then grill them on a gas, charcoal, or grill pan on the stove over medium-high heat until the kernels are evenly charred, about 10 minutes, rotating the cobs as they cook. Once the ears are cool enough to handle, slice the kernels off the cob.

Measure out 3 cups of charred sweet corn kernels then add them to a large mixing bowl with the green onions, red onion, jalapeno, garlic, cotija cheese, and cilantro then stir with a spatula to combine.

To a small bowl add the juice of the lime, mayonnaise, sour cream, chili powder, and salt then whisk to combine.

Pour the dressing over the sweet corn mixture then stir to coat. Scoop the salad into bowls or onto plates then serve. Alternatively you can refrigerate for up to 3 days then serve cold.