Put the oil in a large pot over medium-high heat. When hot, add the pancetta, crisp, and remove with a slotted spoon. Add garlic and onion to pan and sauté, 1 minute.
Peel the potatoes and cut them into large chunks, in half if they're midsized, and leave them whole if they're small.
Add the potatoes to the pan and sprinkle with salt and pepper. Cook, stirring occasionally, until coated in oil and beginning to turn golden.
Add the wine and stock so that the potatoes are barely covered. Bring to a boil, stirring once in a while to make sure the potatoes aren't sticking, then turn the heat to medium-low so that the mixture bubbles gently. Cook, stirring occasionally, until the potatoes get tender, 20 to 25 minutes. Add more liquid if they start to stick. The potatoes are done when a skewer or sharp knife inserted into one meets almost no resistance. Taste and adjust the seasoning, garnish with pancetta and parsley, and serve hot or at room temperature.