Smoked Salmon and Potato Breakfast Casserole

2 cups (lightly packed) 1/2-inch cubes French baguette with crusts 2 tablespoons (1/4 stick) butter 2 tablespoons vegetable oil 1 pound russet potatoes, peeled, cut into 1/2-inch cubes 1/2 cup finely chopped shallots 1/2 pound hot-smoked salmon fillets, skinned, flaked into bite-size pieces 3 tablespoons minced fresh chives 2 teaspoons minced fresh dill 4 large eggs 1 cup half and half 3 tablespoons sour cream 1 teaspoon Dijon mustard 1/2 teaspoon salt 1/4 teaspoon ground black pepper Additional sour cream Capers Fresh dill sprigs

Preheat oven to 400°F. Arrange bread on rimmed baking sheet. Bake until pale golden, about 5 minutes, then cool. Butter 11x7-inch glass baking dish. Melt 2 tablespoons butter with oil in heavy large skillet over medium-low heat. Add potatoes. Stir to coat and arrange in single layer. Cover and cook until potatoes are almost tender, about 8 minutes. Uncover; increase heat to medium-high, and cook until potatoes are lightly browned and tender, stirring occasionally, about 5 minutes. Add shallots and sauté until soft, about 2 minutes. Remove from heat. Gently mix in bread, salmon, chives, and minced dill. Transfer mixture to prepared dish.

Whisk eggs and next 5 ingredients in medium bowl to blend well. Pour custard over potato mixture in dish. Let stand 15 minutes, occasionally pressing bread into custard. (Can be made 1 day ahead. Cover; chill. Let stand at room temperature 30 minutes before baking.)

Preheat oven to 350°F. Bake casserole, uncovered, until custard is set, about 30 minutes. Cut into squares and top with additional sour cream, capers, and dill sprigs; serve hot.

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