Place the potatoes in a very large pot and cover with a generous amount of cold water. Boil until just tender, but still a little firm. When there, add the snap peas, carrot, cauliflower, broccoli and bell pepper; return to a boil, and cook 2 minutes more. Drain well, cool the vegetables in ice-cold water, and then drain well again.
Arrange vegetables in a 9" x 13" casserole. Drizzle with the stock and butter; season with salt and pepper. Cover with foil and refrigerate until ready to reheat (can be made to this point several hours before serving).
When ready to serve, bake the vegetables, covered, in a 350 degrees F oven for 20 to 25 minutes, or until steaming hot. Sprinkle with parsley, if desired, and serve.