If you have a grill at your disposal, grill the corn on the cob to char some of the kernels and then slice all the kernels off the cob. If you don't have access to a grill, slice the corn kernels off the cob and sauté them in a skillet over high heat. Transfer the corn to a bowl and add the mayonnaise, cotija cheese and chili powder.
Substitution for Mexican Crema
½ cup sour cream
¼ cup heavy cream
¼ teaspoon salt
2 teaspoons fresh lime juice