Potato and Fennel Gratin with Gorgonzola, Olives and Tomato-Marjoram Sauce

Preparation Preheat oven to 375°F. Rub inside of 9x9x2-inch metal baking pan with garlic clove. Rub pan with 1/2 tablespoon butter. Cover bottom with 1/4 of potatoes, overlapping slightly. Sprinkle 1/3 of chopped olives over, then 1/4 of cheese. Top with 1/3 of fennel; sprinkle with salt and pepper and 1/3 of marjoram. Dot with 1 tablespoon butter. Repeat layering two more times. Top with remaining potatoes, then half of remaining cheese; dot with re-maining 1 tablespoon butter. Pour milk over; arrange halved olives atop. Sprinkle with salt and pepper. Cover pan with foil. Bake gratin until vegetables are almost tender, about 50 minutes. Remove foil; sprinkle with remaining cheese. Bake uncovered until potatoes are tender and golden, about 25 minutes longer. (Can be made 2 hours ahead. Let stand at room temperature. Rewarm in 350°F oven until heated through, about 20 minutes.) Let gratin stand 15 minutes. Serve with Tomato-Marjoram Sauce.

Preparation Preheat oven to 375°F. Rub inside of 9x9x2-inch metal baking pan with garlic clove. Rub pan with 1/2 tablespoon butter. Cover bottom with 1/4 of potatoes, overlapping slightly. Sprinkle 1/3 of chopped olives over, then 1/4 of cheese. Top with 1/3 of fennel; sprinkle with salt and pepper and 1/3 of marjoram. Dot with 1 tablespoon butter. Repeat layering two more times. Top with remaining potatoes, then half of remaining cheese; dot with re-maining 1 tablespoon butter. Pour milk over; arrange halved olives atop. Sprinkle with salt and pepper. Cover pan with foil. Bake gratin until vegetables are almost tender, about 50 minutes. Remove foil; sprinkle with remaining cheese. Bake uncovered until potatoes are tender and golden, about 25 minutes longer. (Can be made 2 hours ahead. Let stand at room temperature. Rewarm in 350°F oven until heated through, about 20 minutes.) Let gratin stand 15 minutes. Serve with Tomato-Marjoram Sauce.