3poundsred-skinned potatoes, peeled, cut into ¼-inch thick slices
2cupsshredded fontina cheese
1 1/2cupsfreshly grated Parmesan cheese
Preheat oven to 375°F. Butter 13x9x2-inch baking dish. Melt 2 tablespoons butter in large skillet over medium heat. Add leeks and cook until tender, stirring occasionally, about 10 minutes. Add garlic and cook 2 minutes more, stirring frequently. Remove from heat.
Arrange half of sliced fennel in a single layer in prepared baking dish. Sprinkle with 1 tablespoon fennel fronds, half of the parsley, and season with salt and pepper. Arrange half of sliced potatoes overlapping slightly on top of the fennel and herbs. Top potatoes with half of leek mixture. Sprinkle generously with salt and pepper. Sprinkle with half of fontina and grated parmesan cheese. Repeat layering with remaining fennel, fennel fronds, parsley, potatoes, leek mixture, and cheeses. Sprinkle assembled gratin with salt and pepper.
Bring chicken stock and whipping cream to a boil in a medium saucepan. Pour mixture over gratin. Bake uncovered until vegetables are very tender, liquid is almost absorbed and top is deep golden brown, about 1 hour to 1 hour 10 minutes. (Can be prepared 3 hours ahead. Let stand at room temperature covered in foil. Rewarm covered in 375°F oven 20-30 minutes.)
Give it Some Thyme - Potato Leek and Fennel Gratin