1. Position a rack in the top-middle position of the oven and preheat it to 400°. Place the peach halves on a baking sheet and season with salt, pepper and a drizzle of olive oil. Roast the peaches until they are soft but still hold their shape, about 8 minutes. Turn on the broiler and cook until the peaches are browned, about 2 minutes. Remove the pan from the oven and set aside.

2. In a small mixing bowl, add the shallot and cover with the Champagne vinegar. Set aside for 10 minutes.

3. While the shallots macerate in the vinegar, set a large skillet or cast-iron pan over medium heat; heat until hot, 1½ to 2 minutes. Add the pancetta and cook until crisp, about 8 minutes, then transfer to a paper-towel-lined baking sheet. Drain the pan drippings and set aside.

4. To the shallots, add ¼ cup of the olive oil and whisk to combine. Whisk in half of the reserved pancetta drippings (save or discard the rest), season with salt and pepper and set aside.

5. Using a blender or food processor, purée the remaining ¼ cup of olive oil with the sage leaves and a pinch of fleur de sel.

6. To serve, place two peach halves on a plate and sprinkle pancetta over each peach. Toss the arugula with the shallot-pancetta vinaigrette and add a handful of arugula to each plate. Drizzle with the sage oil and serve immediately.