Preheat the oven to 375F.

Combine mushrooms and shallots in a large skillet and place over medium heat.

Cook, stirring frequently, until mushrooms and shallots have released their liquid and browned, about 12 minutes; add wine 1 tablespoon at a time if necessary to keep mushrooms from sticking.

When mushrooms are very tender and browned, add thyme, soy sauce, pepper and any remaining wine.

Cook, stirring, until liquid has evaporated. Set aside.

Combine 3 cups water and salt in a large saucepan and bring to a boil.

Stir in porcini powder.

Add polenta in a thin, steady stream, stirring constantly.

Cook, stirring constantly, until polenta is thickened and bubbles, about 3 minutes.

Remove from heat and stir in mushroom mixture, 3 tablespoons of the parsley and 3 tablespoons of the chives.

Pour polenta mixture into a 9-inch pie plate and smooth the top.

Bake until just browned on top, about 30 minutes.

Cool for 20 to 30 minutes.

Run a table knife around the edge of the pan.

Sprinkle pie with remaining 1 tablespoon parsley and 1 tablespoon chives.

Cut into wedges.

To make the pie ahead, pour the polenta mixture into the pie plate and cool, then cover and refrigerate for up to 2 days. Add about 15 minutes to the baking time.