butter (for greasing the baking dish)
2 cups stale bread (cut into 1/4 inch cubes)
1 pound Earthbound Farm Organic Baby Spinach (about 13 packed cups)
1 cup grated Gruyere cheese
2 tablespoons olive oil or butter
8 ounces fresh shiitake mushrooms (stems discarded, caps cut into 1/4-inch slices)
2 tablespoons minced shallots
3 large eggs
2 cups half & half
1 teaspoon salt
    Freshly ground black pepper