In a small pan, cook the chopped onions and garlic in butter until transparent. Add the rice and mix well to coat the rice grains in oil. Add the wine to the pan and bring to the boil. Top with the beef stock and leave to simmer, stirring continuously. Meanwhile, season the duck breasts with salt and seal, fat side down first in a very hot pan. Do not add any fat to the pan. Continue to cook the duck breasts in a pre-heated oven at 180`c for just 5 minutes. At this stage, add the peach pieces to the pan and cook together for 4 more minutes. When the duck is cooked, remove from the oven. Discard the peaches from the pan before placing the pan on high heat. Add in the port, followed by the beef stock and reduce until you obtain a glossy sauce. Once the rice is nearly cooked and the liquid has been absorbed, add the berries and continue to stir. Finally add the crushed almonds and mascarpone, adjust with salt and pepper and serve underneath the duck breasts. Drizzle over the glossy sauce and serve.