Combine the vinegar, basil, garlic, sugar, 1/2 teaspoon of salt, 1/4 teaspoon of pepper and oil in a blender and blend until smooth or whisk by hand with a wire whisk. This may be prepared 2 hours in advance and refrigerated.
Combine the corn kernels, onion and tomatoes in a large bowl. Add the dressing and toss to coat, season with salt and pepper. Let sit at room temperature 30 minutes before serving.
Top with crumbled blue cheese and garnish with basil sprigs just before serving. Salad may be served at room temperature or prepared one day in advance and served cold.
*Tip: put your block of blue cheese in the freezer for one hour and then grate it over the salad.