This recipe was one of my favorite Lafayette Louisiana dishes. Brian's Grandmother only made this during the holidays. It was quite a treat to get a slice. It was so, very tasty and had a wonderful cajun spice to it.
With your fingers, pick off and discard any bits of fat clinging to the lining of surface of the pig's stomach. Then place the stomach in a deep pot, pour in enough cold water to cover it by at least 1 inch and let it soak for about 2 hours. Rinse the stomach briefly under cold running water and pat it completely dry, inside and out, with paper towels.
Meanwhile, prepare the stuffing in the following manner: Combine the slices of bread and the milk in a bowl and let them stand at room temperature until all the liquid has been absorbed. Place the bread in a sieve and, with the back of a large spoon, press out any excess milk. Discard the milk and set the bread aside.
In a heavy 10-inch skillet, melt the butter over moderate heat. When the foam begins to subside, add the onions, green peppers, scallions and garlic and, stirring frequently, cook for about 5 minutes, or until the vegetables are soft but not brown. With a rubber spatula, scrape the entire contents of the skillet into a deep bowl and let the vegetables cool to room temperature.
When the vegetables are cool, add the reserved bread, the ground pork, yams, egg, red pepper and salt. Knead vigorously with both hands, then beat with a large spoon until the mixture is light and fluffy.
Because the stuffing contains raw pork, fry a spoonful of it in a skillet before tasting it for seasoning. With a large needle and strong white thread, sew up one of the openings of the stomach. Then fill the stomach cavity with the stuffing and sew the other opening securely shut.
Heat the oil over moderate heat in a heavy casserole just large enough to hold the stomach comfortably. Add the stuffed ponce and turn it over with two wooden spoons until it is lightly browned on all sides. Pour in 1 cup of the water and, when it comes to a boil, cover the casserole tightly.
Reduce the heat to moderate and steam the ponce for 3 hours, regulating the heat to keep the water at a simmer. Check the casserole every 20 minutes or so and add boiling water as necessary to keep the liquid at a depth of about ½ inch.
Transfer the stuffed ponce to a heated platter and let it rest for at least 10 minutes for easier carving. Meanwhile, boil the liquid remaining in the casserole until it is reduced to thin gravy with the intensity of flavor you desire. Pour the gravy into a bowl and serve it separately. At the table, carve the ponce crosswise into ¼-inch-thick slices.