Preheat the oven to 350 degrees F.
Insert a thin, sharp knife into the thick side of each chicken breast and make a horizontal pocket, being careful not to cut all the way through to the other side. Cut thick pieces, 3 or 4 tablespoons each, from the refrigerated blue cheese butter and insert into the chicken pockets. Pull the chicken flesh around the butter to enclose the filling. Seal with toothpicks, as necessary.
Lightly salt and pepper both sides of the chicken. Place the flour in a shallow dish and lightly dust the chicken, shaking to remove any excess. In a large skillet, heat the clarified butter over medium-high heat. Add the chicken and sear until golden brown, 2 to 3 minutes on the top side. Turn and place in the oven and bake until the chicken is cooked through, about 12 minutes. Remove from the oven, transfer to a plate and cover to keep warm.
As a snack, spread the remaining blue cheese butter, leftover from the 1 cup, evenly onto the French bread rounds and place on a baking sheet. Preheat the oven to 375 degrees F. Bake until golden brown and bubbly, 8 to 10 minutes. Remove from the oven.
Remove the chicken from the oven. Add the shallots and garlic to the fat remaining in the pan from the cooked chicken and cook over medium-high heat, stirring, for 1 minute. Add the port and bring to a boil, and cook until reduced by half, stirring to deglaze the pan. Add the chicken stock and lemon juice and cook until reduced by half. Reduce the heat to medium-low. Whisk in the butter, 1 tablespoon at a time, adding each piece before the previous one has been completely incorporated. Continue until all the butter is incorporated and the sauce coats the back of a spoon, removing the pan from the heat periodically to prevent the sauce from getting too hot and breaking.
Add the remaining 2 tablespoons of Blue Cheese Butter, whisking until completely incorporated and the sauce is smooth. Return the chicken and any accumulated juices to the pan. Cook until the chicken is warmed through, about 1 minute.
Divide the chicken and pan sauce among 4 large dinner plates. Garnish with the parsley and serve.
Place the toasted bread on a separate platter with watercress.
Yield: 4 servings