Shuck the corn and remove the silks. Slice off one third of the corn kernels all around the cob into a bowl, and then another third. Cut the last third off close to the cob, then scrape the milky juice from the cob into the bowl with the rest of the corn. Add canned milk into the bowl. If corn is dry, add a little more canned milk. In a large heavy skillet, melt the butter on low heat. Sauté the onion until translucent. Add the corn, sugar, salt, and black pepper. Cook over low heat for 10 minutes, stirring frequently. Yield 6 servings