Arrange two oven racks so that one is in the center and the other 4-6 inches below it. Preheat oven to 450F (225C).
To make the potatoes: Put the potatoes in a large bowl. Pour over chicken stock, lemon juice, olive oil, salt and oregano. Toss around to coat with the seasonings. Dump everything onto a large rimmed baking sheet in an even layer, cut sides down.
Slide the potatoes onto the lower oven rack and roast 55-60 minutes, or until fork-tender and the edges are golden brown. Check the potatoes after 45 minutes to be sure they aren't getting too brown.
Spread the leek and shallot over the bottom of a 13 x 9 x 2-inch (2-quart) baking dish. Season the chicken very generously on both sides, then arrange it on top of the leeks and shallots. Pour over the wine and olive oil. Scatter the tomatoes over the chicken and sprinkle with the fennel and chili.
Put the chicken on the middle rack and roast 45 minutes. The chicken should be tender and cooked through, and the tomatoes burst and juicy.
Serve the chicken with the potatoes, sprinkled with parsley, black pepper and feta cheese if you like.
Storing leftovers: The chicken and potatoes taste delicious the next day (and day after). Wrap the baking dish with foil and refrigerate.
If you'd rather substitute chicken breasts, use four breasts and reduce the baking time to 25-30 minutes. Run the dish under the broiler for a few minutes if you want to brown the chicken and tomatoes before serving.