Preheat the oven to 350 degrees . Butter a 1-1/2-quart souffle or casserole dish and set aside. Season the mushrooms with salt and pepper; set aside.
In a saucepan, bring the cream and milk to a simmer. Remove from the heat and whisk in the cornmeal until smooth. Add the leeks and mix well. Let cool slightly.
Stir the mushrooms, cheese, soy sauce and hot pepper sauce into the cornmeal mixture. Stir in the egg yolks and mix well.
Using an electric mixer or whisking by hand, beat the egg whites until stiff peaks form. Stir about one-third of the whites into the cornmeal mixture, then gently fold in the remaining whites. Scrape the batter into the prepared dish.
Bake until the top is puffed and brown and a knife inserted in the center comes out mostly clean, about 1 hour. Serve immediately (the top will deflate slightly as it sits).