1) Butter the bottom and sides of a 22 by 27-cm baking tray and set aside.
2) Heat the oil in a medium saucepan over high heat. Add the onion and cook until soft, about 3 minutes. Add the garlic and cook for 30 seconds. Add the wine and cook until completely reduced.
3) Add the stock and bring to the boil. Slowly whisk in the polenta, stirring until it begins to thicken. Season with salt and pepper, reduce the heat to medium, switch to a wooden spoon, and continue cooking and stirring until the mixture is smooth and soft, about 20 minutes. If the mixture becomes too thick, stir in some water, it should be a pourable consistency.
4) Stir in the corn kernels and pour the mixture into the prepared pan and spread evenly. Cover and refrigerate until firm, at least 2 hours and up to 24 hours. Cut the polenta mixture into even squares.
5) Heat the grill to high. Brush the cakes on both sides with some of the oil and season with salt and pepper. Grill the cakes until golden brown and slightly charred on each side, about 1 1/2 minutes per side. Remove to a plate and top each cake with some of the relish.
For the grilled corn-green chile relish:
1) Combine the corn, chiles, onion, lime juice, honey, oil and coriander in a medium bowl and season with salt and pepper. Let the relish sit at room temperature for at least 30 minutes before serving. The relish can be made 8 hours in advance and refrigerated. Bring to room temperature before serving.