In 2-cup heatproof liquid measuring cup, cover dried mushrooms with 1 cup boiling water and let soak. Cook egg noodles per package directions.

Meanwhile, heat ½ tablespoon oil in large skillet on medium-high. Add one-third of fresh mushrooms and ¼ teaspoon each salt and pepper; cook, tossing twice, until golden, 3 to 4 minutes. Transfer to large plate. Repeat twice more with 1 tablespoon each oil, one-third of remaining fresh mushrooms and ¼ teaspoon each salt and pepper. Add half of mushroom soaking liquid to pan and cook, scraping up any browned bits, then pour liquid from pan into measuring cup.

Wipe out skillet, then heat remaining tablespoon oil on medium. Add onion and ¼ teaspoon each salt and pepper and cook, stirring occasionally, until golden brown and tender, 3 to 4 minutes. Remove porcini mushrooms from liquid and chop; reserve soaking liquid.

Stir garlic into onions and cook 1 minute. Add wine and thyme sprigs and cook, scraping up any browned bits, 1 minute. Add mushroom liquid (about ¾ cup) and miso, stir to dissolve and simmer until slightly reduced, 3 to 4 minutes.

Remove skillet from heat and discard thyme sprigs. Stir in sour cream and soy sauce. Fold porcini mushrooms and cooked mushrooms into sauce, then fold in noodles to coat. Serve sprinkled with parsley and additional thyme leaves.