To prepare the hens: Remove the dark meat from the legs and chop it very finely. Lay the main part of each bird flat, skin-side down. There will be a rough rectangle of skin with the two breasts and their smaller fillets attached at the top. Remove one small fillet and lay it between the breasts to fill the indentation. Use the other to fill any other gaps. Lay a piece of plastic over top, and pound the whole flat. Remove the plastic. Push the meat around a little, if you need to, to achieve and even square of white meat, roughly centered on the skin. Season the hens with salt, and pepper. To make the stuffing: Heat 3 tablespoons of the butter, and saute the onion until soft. Add the garlic and saute for 1 minute more. Remove the onion mixture to a bowl. Heat the remaining butter in the pan, and toast the bread crumbs. Add them to the onions. Stir in the figs, Cognac, and thyme. Season the mixture with salt, and pepper.
Preheat the oven to 325 degrees F.
Lay the prosciutto slices, slightly overlapping, on a piece of foil. Lay 1 bird on top, and season with salt, and pepper. Spread over the half the stuffing, and then roll into a log. Wrap in foil, twisting the ends to make a tight cylinder. Repeat with the other hen. Bake 30 minutes. Remove the foil, and return to the oven 10 minutes longer. Remove. Let rest 10 minutes before slicing to serve with Watercress Salad.
In a medium bowl, toss the greens with the oil, vinegar, salt, and pepper, to taste. Arrange on a serving platter and scatter over the almonds and grapes. Serve.