Preheat the oven to 225C/425F/Gas 7.
For the chicken, using a sharp knife, carefully cut into the side of the chicken breast to create a pocket. Stuff the pocket with the Brie and tomatoes. Press down to seal the stuffing inside.
Wrap the stuffed chicken breast with the speck slices.
Place a splash of oil in an ovenproof pan over a high heat. Place the speck-wrapped chicken breast into the pan and cook the chicken for one minute on each side, to brown. Transfer into the oven to roast for 15-20 minutes, or until cooked through.
For the squash wedges, place the oregano, turmeric, curry powder and oil into a large bowl. Add the squash and mix well to coat. Place into on a roasting tray and place into the oven to roast for 15 minutes, or until cooked through. Turn the squash occasionally, so that it will brown evenly.
For the sauce, place the red onion in a saucepan over a high heat. Add the red wine and beef stock and bring to the boil. Reduce the heat to a simmer and cook until the liquid has reduced by half.
Add the butter to the sauce and remove from the heat. Stir the butter into the sauce to give a glossy finish.
To serve, place the chicken onto a plate with a pile of squash wedges and drizzle the sauce around.