How to Make It
Heat the oil in 2 large nonreactive skillets. Season the guinea hen breasts on both sides with salt and pepper. Add 3 breast halves to each skillet, skin side down, and cook over high heat until well browned, about 5 minutes. Turn and cook until the other side is browned, about 2 minutes; transfer to a platter. Brown the remaining breasts in the 2 skillets.
Add the pancetta to the skillets. Cook over low heat, stirring, until lightly browned, about 4 minutes. Using a slotted spoon, transfer the pancetta to a small plate. Divide the mushrooms between the skillets and season with salt and pepper. Raise the heat to moderately high and cook, stirring occasionally, until browned and any exuded liquid has evaporated, about 8 minutes. Transfer the mushrooms to a large plate.
Return the pancetta to the skillets and add the shallots. Cook over moderately high heat, stirring, until wilted, about 3 minutes. Add 1 cup of wine to each skillet and boil until almost evaporated, about 8 minutes. Scrape the mixture from the skillets into a large, heavy roasting pan and add the mushrooms.
Preheat the oven to 450°. Set the roasting pan on 2 burners over moderately high heat. Add the carrots, chicken stock and thyme and bring to a simmer. Arrange the guinea hen breasts on top, skin side up, and roast in the oven for about 12 minutes, or until just cooked through. Transfer the breasts to a clean platter and cover with foil to keep warm.
Set the roasting pan on 2 burners over high heat, add the peas and boil until the peas are tender and the cooking juices are reduced to 1 1/2 cups, about 8 minutes. Pour in any accumulated juices from the hens. Remove the pan from the heat, stir in the butter and season with salt and pepper.
Set the guinea hen breasts on large plates and spoon the red wine sauce and vegetables around the breasts. Serve at once.