Preheat the oven to 400 degrees F. Line a small baking sheet with aluminum foil and set aside.
Toast the bread until light golden brown on both sides. Trim the toast using a 4-inch round cookie cutter and using a pastry brush, lightly coat 1 side of each toast with 1/2 teaspoon of the melted butter. Set aside on a wire rack to crisp. Reserve trimmed crusts and crumble into coarse bread crumbs to be used as garnish.
In a large nonstick skillet or saute pan sear the ham slices until lightly golden, about 1 minute.
Season each chicken breast with 1/4 teaspoon of the Essence and season lightly with salt and pepper.
In the already hot large skillet or saute pan, heat the oil over high heat. Add the chicken and sear until lightly colored, about 1 1/2 minutes per side. Transfer the chicken to the prepared baking sheet and cook until cooked through, 12 to 14 minutes.
While the chicken breasts are finishing in the oven, make the pan sauce: Return the skillet to medium-high heat and melt 2 tablespoons of the butter in the fat and juices remaining in the pan. When the butter is foamy, add the shallots, salt, and pepper and cook, stirring, until the shallots are soft, about 2 minutes. Add the garlic and herbes de Provence and cook, stirring, for 30 seconds. Add the tomato paste, wine, and tomatoes; bring to a boil, and cook, stirring, until the wine is reduced, about 1 minute. Add the stock, return to the boil, and cook until the mixture is reduced by half, about 8 minutes.
Add the heavy cream, stir, and place the chicken breasts in the pan. Top each chicken breast with a piece of ham and baste with the sauce; continue to cook until sauce is thick enough to coat the back of a spoon, about 5 minutes. Reduce the heat to low and swirl in the remaining 4 tablespoons butter, a piece or 2 at a time. Remove from the heat, adjust the seasoning to taste, and cover to keep warm until ready to serve.
To serve, place 1 toast round in the center of 4 large plates and place 1 ham-topped chicken breast on top. Drizzle each portion with the sauce, garnish with chopped fresh parsley and the reserved bread crumbs and serve immediately.
Yield: 4 servings