How to Make It
Heat the oven to 425°. In a medium frying pan, melt 1 tablespoon of the butter over moderately low heat. Add the Swiss chard and cook until starting to wilt, about 1 minute. Stir in the garlic and 1/8 teaspoon each salt and pepper. Cook until no liquid remains in the pan, about 2 minutes.
Butter an 8-by-8-inch baking pan or similarly sized gratin dish. Layer one third of the potatoes in the dish and top with 1/8 teaspoon each salt and pepper, a third of the cheese, and half the Canadian bacon. Spread the Swiss chard in a single layer. Top with half the remaining potatoes and sprinkle with 1/8 teaspoon each salt and pepper. Spread half the remaining cheese and the remaining Canadian bacon over the potatoes. Add the remaining potatoes to the dish, sprinkle with the remaining 1/8 teaspoon each of salt and pepper, and top with the remaining cheese and 1 tablespoon butter. Pour the chicken broth over all.
Cover the gratin with aluminum foil and bake for 15 minutes. Remove the foil and continue baking until the potatoes are tender and the top is golden brown, about 30 minutes longer. Let stand 2 to 3 minutes before cutting.