Preheat the grill. Toss the tomatoes with the olive oil and season with salt and pepper to taste. Grill the tomatoes, until the skins are blackened. Remove and chop coarsely. Place the tomatoes in a blender and add the garlic, onion, balsamic vinegar and basil and blend until smooth. Slowly add the olive oil until emulsified and season with salt and pepper to taste. Reserve

Butter a large shallow baking dish generously with butter, set aside. Place the chicken stock in large saucepan and bring to a boil. Slowly add the polenta, whisking constantly with a wire whisk. Cook over low heat, stirring constantly with a wooden spoon until thickened and smooth. Fold in the corn, Parmesan cheese and parsley and pour the mixture into the prepared baking dish. Cover and chill in the refrigerator at least 4 hours or overnight.

Preheat the grill. Cut the chilled polenta into 2-inch circles, brush with olive oil and season with salt and pepper. Grill on both sides until golden brown. Drizzle with vinaigrette.