Prep: 25 minutes; Chill: 8 hours; Bake: 50 minutes.
1. Place bread pieces in a lightly greased 13- x 9-inch baking dish, and set aside.
2. Cook bacon over medium-high heat in a large skillet 15 minutes or until crisp, stirring occasionally. Remove bacon from pan, and drain on paper towels, reserving about 2 tablespoons drippings in skillet.
3. Add mushrooms, and sauté 10 minutes or until tender. Add 2 tablespoons mustard, and cook 1 minute more. Drain any excess liquid from pan. Transfer mushroom mixture to reserved baking dish; add bacon and basil, and toss with bread until evenly distributed. Sprinkle evenly with cheese.
4. Whisk together remaining 1 tablespoon mustard, eggs, and next 4 ingredients in a large bowl. Pour over bread mixture, cover with foil, and chill at least 8 hours or overnight.
5. Preheat oven to 350°. Remove bread pudding from refrigerator, and bake, covered with foil, at 350° for 35 minutes. Uncover and bake 15 to 20 minutes more or until light golden brown.