Preheat the oven to 375 degrees F. With kitchen shears or a knife, cut along either side of the hen's backbone and remove. Press the hen flat, skin-side down. Cut in half down the middle of the breastbone. Place the hen halves skin-side up in a roasting pan; season with salt and pepper. Roast 30 minutes. While the hen roasts, place the jam, soy sauce, vinegar and water in a small saucepan. Bring to a simmer and stir until the jam is melted and well combined with the other ingredients. Strain the mixture through a fine sieve into a bowl. Mix in the ginger and tarragon. When the hen halves have roasted 30 minutes, baste with half the glaze. Roast 10 minutes more, and then baste with remaining glaze. Roast 10 minutes more, or until cooked through.