Step 1Heat milk in saucepan over medium heat until bubbles form around edges. Stir in polenta and cornmeal and whisk until thickened, about 3 to 4 minutes. Cool about 10 minutes, then stir in egg yolks, butter, salt and baking powder.
Step 2Beat egg whites with sugar until stiff, 2 to 3 minutes. Lightly fold half egg white mixture into polenta. Fold in remaining egg white mixture. (Always add egg white in 2 or more steps to evenly incorporate). Pour polenta mixture into well-oiled 2-quart baking dish or souffle dish. Bake at 350 degrees until polenta is puffy and browned, 45 to 50 minutes.
Step 1Heat oil in skillet over medium-high heat. Add mushrooms with shallots and saute until tender, 5 minutes. Add Madeira and stock. Cook over medium heat until reduced and slightly thickened, 5 minutes. Stir in tarragon, butter and salt and pepper to taste.
Step 2Pour mushroom ragout onto serving platter and spoon Souffle over top.