Blanch large, fairly flat escarole leaves in boiling salted water, just until wilted, about 3 seconds. Gently tap the heavy bases to flatten and soften fibers.
Wrap, eggroll-style, around soft white cheese, such as fresh mozzarella. Brush with oil.
Pre-heat the grill.
In a blender, puree the diced tomatoes with the onions and garlic, and sun-dried tomatoes, if using.
Heat about a tablespoon of olive oil in a skillet. Pour the tomato puree into the oil and cook and stir for about 3 minutes. Season with the balsamic vinegar and salt to taste. Set aside.
Grill the escarole cheese packets jut to warm them and melt the cheese a bit.
Serve with the tomato sauce.