For the polenta: combine ingredients in a 6 cup baking disk and place in a 350° oven. Check and stir after 25 minutes. Cook an additional 15-25 minutes until polenta is set. Stir a couple of tablespoons of grated Parmesan or Asiago cheese into the warm polenta if desired.
For the mushrooms: put the dried mushrooms in a small bowl, and cover with about 1/2 cup boiling water. Allow to steep for 20 minutes. Remove the mushrooms, and pat dry, then chop roughly. Reserve the mushroom stock.
Melt 2 tablespoons of the butter in a sauté pan set over high heat until it has melted. Add the garlic and cook until it starts to sizzle, about 30 seconds. Do not let the garlic brown.
Add the fresh and reconstituted mushrooms and thyme to the pan, and sauté 3 to 4 minutes, turning until browned. Add about 1/4 cup of the mushroom stock to deglaze the surface, using a wooden spoon to scrape at the browned bits. Allow the stock to reduce by half, then turn the heat to medium-low and add the remaining 3 tablespoons of butter, whisking to combine, followed by the soy sauce, cream and olive oil. Allow mixture to cook until it thickens a little, then remove from heat. Taste for seasoning, adding black pepper, if desired.
Put the polenta in a warmed bowl, then top with mushrooms and the sauce. Serve immediately.