Grill the corn according to this recipe. Slice the kernels off the cobs and set aside to cool.: The air should smell faintly sweet with char as the corn sears, and the kernels will take on small brown flecks that indicate caramelization, which deepens taste; aim for even charring across each ear and rotate the cobs as needed, avoid direct flame that burns too quickly because overly blackened kernels become bitter and can overpower the dip.
In a large bowl, mix together the Greek yogurt, mayonnaise, lime juice, garlic powder, onion powder, and salt. Set aside some of the corn, scallions, and jalapeño for topping the dip, then add the remaining corn, scallions, and jalapeño to the bowl and stir to coat. Chill for at least 1 hour.: You will hear a soft snapping as the kernels release from the cob, and the kernels should look plump and glossy, slightly steaming if still warm; cooling prevents the creamy base from thinning, and a common mistake is adding piping hot kernels which can make the dip watery.
To serve, spread the chilled corn dip in a shallow dish and top with the reserved corn, scallions, and jalapeño. Sprinkle with the cheese and drizzle with hot sauce, if desired. Garnish with cilantro and serve with tortilla chips.: As you whisk, the mixture should become smooth and slightly glossy, with the aroma of lime brightening the dairy notes; this emulsified base clings to the corn and seasoning, and if you under season now the final dip will taste flat, so taste and adjust.
Set aside some of the corn, scallions, and jalapeño for topping the dip: Reserve a colorful sprinkle by scooping a few tablespoons of each into a small bowl, their textures should be fresh and crisp, and this reserved mixture creates contrast when served; forgetting to reserve toppings removes the visual and textural finish that makes the dip pop.
Add the remaining corn, scallions, and jalapeño to the bowl and stir to coat: When folded in, the kernels will glisten and the mixture will release a bright, savory scent, the even coating ensures each chip scoop gets balanced flavor, and a pitfall is overmixing which can bruise the kernels and make the dip mushy.
Chill for at least 1 hour: Chilling lets the flavors knit together and the texture firm slightly, the dip will cool to a pleasant, refreshing temperature and the aromas will settle, and rushing this step will give you a dip that tastes disjointed rather than harmonious.
To serve, spread the chilled corn dip in a shallow dish and top with the reserved corn, scallions, and jalapeño: The presentation should be layered, with the reserved bits adding height and crunch, and a shallow dish increases surface area so every chip finds a topping, do not mound too high or it will be hard to scoop cleanly.
Sprinkle with the cheese and drizzle with hot sauce, if desired: The crumbly Cotija cheese will add a salty finish and the hot sauce introduces a glossy streak of heat, both change the palate in pleasing ways, and overdoing the sauce can mask the sweet corn so add sparingly.
Garnish with cilantro and serve with tortilla chips: The fresh green of cilantro brightens each spoonful and the sturdy tortilla chips provide contrast in crunch and neutrality in flavor; serve immediately so the chips remain crisp and avoid leaving the dip out in hot sun for long periods which can affect texture and safety.