Remove the husks and silk from the corn. Pat the cobs dry, then rub lightly with neutral oil and season with kosher salt. The corn must be dry before grilling. Wet corn steams before it chars, and this recipe needs visible caramelised blackened spots. A thoroughly dried cob lets the grill's direct heat go straight into browning the kernel surface, rather than first evaporating lingering moisture — that delay is exactly what produces pale, dull kernels instead of the deep charred spots this dish depends on.

Preheat a grill, grill pan, or cast-iron skillet over medium-high to high heat until very hot. Grill the corn for 10–12 minutes, rotating every 2 minutes, until the kernels are tender and charred in dark patches. Brush with melted butter during the final 2 minutes of cooking so the kernels turn glossy and the butter picks up some smoky charred flavour. Do not fully burn the corn. You want scattered blackened spots and deep yellow kernels, not dry bitter cobs. Brushing the butter on only near the end, rather than at the start, keeps it from burning over the full 10–12 minute grill time while still giving it enough contact with the hot kernels to pick up real smoky char flavour.

Transfer the grilled corn to a board and let cool for 2–3 minutes, just until safe to handle. Stand each cob upright and cut the kernels off with a sharp knife. Keep the knife close to the cob so you get full plump kernels. Do not scrape aggressively into the cob or the mixture will become starchy and mushy. Cutting close rather than scraping is a deliberate texture choice — the cob's core carries a different, starchier consistency than the kernels themselves, and pulling that material into the mix along with the kernels changes the finished texture from creamy-with-distinct-kernels to something closer to a thick, gluey paste.

In a large bowl, mix the mayonnaise, crema or sour cream, lime juice, grated garlic, salt, and black pepper until smooth. Add the warm grilled corn kernels and fold until fully coated. The heat from the corn should loosen the mayo, melt the butter residue into the mixture, and create a glossy wet coating. The mixture should look creamy and abundant, not dry. If it feels too thick, add a small spoonful of crema or a few drops of lime juice. Adding the kernels to the base while genuinely warm, rather than letting them cool first, is the whole reason this mixture ends up glossy rather than thick and separate — the residual heat is doing real work here, actively melting and loosening the fats in the mayonnaise and any clinging butter.

Mix the chilli powder, smoked paprika, and cayenne if using. Keep it ready with the cotija and cilantro before filling the cups. Having every garnish measured and within reach before the corn is even off the grill means the whole assembly sequence, from cutting kernels to topping the filled cups, moves without interruption while everything is still warm.

Divide the creamy corn mixture between 4 cups, using the kernels from 1 cob per cup. Pack generously but do not press it flat. Top each cup heavily with crumbled cotija. Dust with the chilli mixture so the red-orange colour is clearly visible, especially on the top layer. Scatter fresh cilantro over each cup. Packing generously without pressing flat preserves some volume and texture in the cup rather than compacting the corn into a dense, uniform mass — the goal is an abundant, slightly loose pile that still holds its shape.

Place one lime wedge on the rim or edge of each cup. Serve immediately while the corn is still warm and glossy. Positioning the lime wedge on the rim, visible and ready, signals that a final squeeze right before eating is part of how this dish is meant to be finished, brightening the rich, creamy corn underneath.