Surprise Stuffed Chicken Breasts with Tangy Sauce

For Sauce: Melt butter in heavy medium saucepan over medium-low heat. Add onions; sauté until beginning to brown, about 10 minutes.

Add sugar. Sauté until onion is golden brown, about 10 minutes. Increase heat to medium-high. Add vinegar; boil 2 minutes. Add both broths; boil until liquid is reduced to 1 1/2 cups, about 25 minutes.

For Chicken: Soak dried fruit in hot water to cover for 15 minutes. Drain.

Melt 1 tablespoon butter in heavy medium skillet over medium-high heat. Add mushrooms and sauté until tender, about 4 minutes. Add tomatoes and sauté until almost all liquid evaporates, about 4 minutes. Stir in fruit and sauté 2 minutes. Season with salt and pepper.

Steam spinach until just wilted, about 2 minutes. Cool.

Using sharp knife, cut horizontal slit 3/4 of the way through each chicken breast. Open and sprinkle with salt and pepper. Place thin layer of spinach over half of each breast. Top spinach with 2 tablespoons fruit mixture. Close breasts over filling. Tie with kitchen string.

Preheat oven to 425°F (220°C).

Melt 1 tablespoon butter in large skillet over medium-high heat. Sprinkle chicken with salt and pepper; brown in skillet, about 4 minutes per side. Transfer to baking sheet. Bake until chicken is cooked through, about 15 minutes.

Bring sauce to simmer. Remove from heat. Gradually add 4 tablespoons butter, whisking just until melted.

Remove string from chicken. Cut each breast crosswise into 5 slices. Serve with the sauce.