Step 1

Preheat oven to 375°F. Arrange bread pieces in a single layer on a large rimmed baking sheet. Bake 10 minutes. Turn off oven; let bread stand in oven until crisp and dry on the outside and chewy on the inside, 5 minutes.

Step 2

Meanwhile, melt butter in a large skillet over medium. Add onion and mushrooms. Cook, stirring occasionally, until onion is slightly softened, about 4 minutes. Add collards and ½ teaspoon each of the salt and pepper. Cover and cook, stirring occasionally, until collards are wilted, about 5 minutes. Stir in artichoke hearts; cover and cook 3 minutes. Uncover; let cool slightly, about 5 minutes.

Step 3

Whisk eggs in a large bowl until lightly beaten. Add half-and-half, spreadable cheese, 1 cup of the Swiss cheese, and remaining ½ teaspoon each salt and pepper. Whisk until well blended. Add toasted bread and collard mixture; toss well to combine. Spoon into a 13- x 9-inch baking dish greased with butter. Sprinkle evenly with remaining 1 cup Swiss cheese. Cover with aluminum foil; chill at least 7 hours or up to 12 hours.

Step 4

Preheat oven to 350°F. Let the casserole stand at room temperature 30 minutes. Uncover; bake until cheese is browned in spots and filling is set, about 45 minutes. Let stand 5 minutes before serving.