Step 1Peel and seed the pumpkin. Cut the flesh into 1-inch cubes.
Step 2In a large skillet, heat the oil over moderate heat. Add the garlic and fry for a few seconds without browning. Add the pumpkin and fry 1 minute, shaking to coat the cubes with oil. Add the stock, fish sauce and sugar and mix well. Bring to a rapid boil. Cover the pan, reduce the heat to low and simmer 20 to 25 minutes, until the pumpkin is tender but not mushy and the sauce is reduced to about 2 tablespoons. If there is still too much liquid in the pan, raise the heat and boil uncovered to reduce it to a glaze.
Step 3Sprinkle the pumpkin with black pepper to taste and serve at once, over rice if you like.