How to Make It
Butter a 9-by-13-inch baking dish. In a medium saucepan, bring the chicken stock to a boil. Gradually whisk in the polenta until smooth. Cook over moderately low heat, stirring often with a wooden spoon, until the polenta pulls away from the side of the pan, about 15 minutes. Remove from the heat and beat in the Roquefort, butter and parsley. Season with salt and pepper. Pour the polenta into the prepared baking dish and smooth the top. Cover with plastic wrap and refrigerate until firm, at least 2 hours or overnight.
In a small skillet, toast the pumpkin seeds over moderate heat until lightly browned, about 4 minutes. Transfer the seeds to a plate to cool completely.
Melt the butter in a large enameled cast-iron casserole. Add the shallots and garlic and cook over moderate heat, stirring occasionally, until softened but not browned, about 3 minutes. Add all of the mushrooms and season with salt and pepper. Cook over moderately high heat until the mushroom liquid has evaporated and the mushrooms are lightly browned, about 8 minutes. Add the sage and wine and cook until the liquid has reduced by half, about 2 minutes. Add the stock and simmer for 2 minutes, then add the cream and simmer until slightly thickened, about 2 minutes longer. Season with salt and pepper and stir in the parsley. Remove from the heat and keep warm.
Preheat the oven to 350°. Cut the polenta crosswise into 8 strips. Heat 1 tablespoon of the olive oil in a large nonstick skillet. Add 4 of the polenta strips and cook over moderate heat until browned on the bottom, about 3 minutes. Using a long spatula, carefully turn the polenta and brown on the other side. Transfer the polenta to a baking sheet and keep warm in the oven while you heat the remaining 1 tablespoon of olive oil and brown the remaining strips. Set a polenta strip on each plate and spoon the mushrooms over the top. Sprinkle with the pumpkin seeds and serve.