Chop the challah bread into 1/2-inch cubes to make 16 cups. Stale bread works best for stuffing-if yours is fresh, spread out the cubes on baking sheet and dry in a 300 degrees F oven, 15 to 20 minutes.
Heat 1 stick butter in a large skillet over medium heat. Add the onions, celery, sage, thyme, and salt and pepper to taste. Cook, stirring, until the vegetables are tender, about 5 minutes. Add the chicken broth; bring to a simmer and remove from the heat.
Meanwhile, cook the wild rice as the label directs. Beat the eggs and parsley in a large bowl; stir in the bread cubes, the vegetable-broth mixture, the prepared rice and the mushrooms. Stir in the raisins.
Transfer the mixture to a buttered 3-to-4-quart baking dish and dot with the remaining 2 tablespoons butter. Cover with foil and bake at 375 degrees F, 30 minutes. Uncover and bake until golden, about 20 more minutes.