Preheat the oven to 220C/gas 7/fan 200C. Score the duck breasts on their skin side with a very sharp knife, then press the cracked pepper on to the skin and sprinkle with the salt. Heat a heavy-based frying pan until it is very hot, then put the breasts skin-side down in the hot pan, without added fat. Cook for 5-6 minutes until the skin is crisp, then turn and cook on the other side for 2 minutes. Transfer the duck breasts, skin-side up, to a baking tray, pour the fat into a bowl and wipe the frying pan clean. Roast the duck for 8-10 minutes, depending on thickness.
While the duck is roasting, prepare the vegetables. Cook the potatoes in boiling salted water for 10 minutes. Remove the duck breasts from the oven and set aside to rest for about 10 minutes. After the potatoes have cooked for 10 minutes, tip in the broad beans and cook for 1 minute, then add the peas and cook for 3-4 minutes until all the vegetables are tender. Drain well.
Heat half the duck fat in the frying pan until hot, and cook the bacon until browned, about 4 minutes. Toss in the garlic and veg until piping hot and glossy. Pour in the vinegar, let it bubble, then stir in the parsley, and season with salt and pepper. Serve with the duck.