Place the potatoes in a large saucepan and cover in cold water. Add a pinch of salt, and bring to a boil over medium-high heat. Boil until tender, 10-15 minutes depending on size. Drain, and return to the saucepan. Smash them lightly with a fork to break them up a little. Set aside.

Preheat oven to 400℉.

Place approximately 3/4 of the oregano in a blender or food processor. Add a pinch of salt, black pepper, the olive oil and red wine vinegar. Pulse until pureed, and set aside.

Slice each chicken thigh into 3 strips and place in a shallow bowl. Sprinkle with salt and pepper and set aside.

Heat a large skillet over medium-high heat. Add the diced pancetta and fry until crisp. Use a slotted spoon to transfer the pancetta to a paper towel-lined plate. Add the chicken to the skillet, fitting it all into a single layer (cook in batches if you need to). Fry in the pancetta fat over high heat for about 10 minutes, tossing occasionally, until almost cooked through. Use the slotted spoon to transfer to a casserole dish. Add the cooked potatoes to the casserole, along with pancetta, tomatoes, and remaining oregano leaves. Drizzle with prepared oregano sauce, and toss to combine. Bake for 40 minutes, until golden.