Preheat the oven to 350 degrees F. Place the bread cubes on a sheet pan and bake for 15 minutes, tossing once, until lightly browned. Place the pancetta in one layer on another sheet pan and bake in the same oven for 15 to 20 minutes, until lightly browned. Place the pancetta on a plate lined with paper towels and set aside.
Soak the leeks in water until they're clean, and spin them dry in a salad spinner. Heat the butter in an 11-inch pot over medium heat; add the leeks and cook for 10 minutes, stirring occasionally. Add the wine, 1 teaspoon salt and 1 teaspoon pepper and cook for 5 minutes, until the wine almost evaporates and the leeks are tender. Off the heat, mix in the artichokes, toasted bread cubes, chives and tarragon.
Whisk the eggs, cream, chicken stock, nutmeg and 1 teaspoon salt together in a large bowl. Spoon half of the bread mixture into a 9-by-13-by-2-inch baking dish. Sprinkle with half the Emmentaler and add the remaining bread mixture. Pour on the cream mixture, sprinkle with the remaining Emmentaler and press lightly to help the bread absorb the liquid. Dice or crumble the pancetta, scatter on top and sprinkle with pepper. Set aside at room temperature for 30 minutes to allow the bread to absorb the cream mixture. Bake for 45 to 50 minutes, until the custard is set and the bread pudding is puffed and golden. Serve hot.