Mushrooms, roasted until tender, soak up flavor and moisture from a bright vinaigrette.
Preheat oven to 450°F. Gently wipe dirt and moisture from mushrooms using a clean towel. Use a bird's beak knife to trim any bruised or dried-out areas of mushrooms and to remove any dirt from gills. Roughly break up hen-of-the-woods mushrooms into bite-size pieces. Toss together cremini mushrooms and 1/4 cup oil in a large bowl; using a slotted spoon, transfer creminis to a baking sheet. Add hen-of-the-woods mushroom pieces, chanterelles, and 1/2 cup oil to bowl, and toss to coat. Using a slotted spoon, transfer mushroom mixture to a separate baking sheet.
Place baking sheets in preheated oven, and roast until mushrooms are golden brown, 20 to 25 minutes. Remove from oven. Sprinkle creminis with 1/4 teaspoon salt; sprinkle hen-of-the-woods and chanterelle mushrooms with 1/4 teaspoon salt. Let cool to room temperature, about 5 minutes. Cut large creminis lengthwise into quarters.
Whisk together Champagne vinegar, shallot, thyme, pepper, 3/4 teaspoon salt, and remaining 1/2 cup oil in a large bowl. Add mushrooms; toss to coat. Let stand at room temperature 2 hours. Sprinkle with remaining 1/4 teaspoon salt, and drizzle with lemon juice. Serve with grilled bread.