Slice the corn off the cob into a large bowl, getting all of the pulp. Set aside. Combine 1 tablespoon cornstarch with 1/2 cup water, and set aside. In the large bowl of corn, combine corn, 1/4 teaspoon salt, 1/2 teaspoon sugar, and the cornstarch/water mixture. Stir. Now, melt 3 tablespoons of butter or margarine in a medium saucepan. Add the corn mixture, and cook over low heat, stirring occasionally. You may add any or all of the additional 1/2 cup water as the corn mixture begins to thicken. Just keep stirring, and making sure that it is smooth. Sweet, young, tender corn will cook in about 5 minutes. More mature corn will take up to 10 minutes. You may want to taste test the corn for flavor and doneness. When done to your liking, pour the corn into a nice serving bowl. Serve immediately--add a little extra butter on top, if you like!!! Corn has super fantastic flavor made this way!