Boil the potatoes in a large pot of salted water until tender. Drain, peel, and slice into a large bowl. Meanwhile, cook the peas in a saucepan of boiling salted water until tender. Rinse immediately under cold water, drain, and set aside.
Fry the bacon in a frying pan. When crisp, add the onion and garlic, and stir to warm through. Pour over the vinegar to deglaze, scraping up the good bits from the bottom of the pan. Stir in the stock and oil. Add the peas to warm through. Then combine all with the potatoes in the bowl. Season with salt and pepper, and serve.