Salad:
Preheat oven to 400º Fahrenheit
Place trimmed Brussels sprouts, 2 tablespoons olive oil, kosher salt, and pepper in a large bowl and combine well. Place on roasting pan. Roast for 30 to 45 minutes, rotate sheet pan halfway through cooking for even browning. Brussels sprouts should be crispy on the outside with some charred spots and tender on the inside. Remove from oven and transfer to a cooling rack over a baking sheet (the air circulating underneath the rack will keep the brussels crispy). Set aside until ready to use.
Heat remaining olive oil in a large skillet over medium-high heat. Add mushrooms (in batches) and cook without stirring until undersides are golden brown, about 3 minutes. Season mushrooms with salt and pepper, toss, and continue to cook until both sides are golden brown, about 3-5 minutes. Reduce heat to medium and add thyme sprigs, garlic, and butter to skillet. Baste mushrooms with foaming butter; cook until butter smells nutty. Using a slotted spoon, transfer mushrooms to a small bowl, leaving thyme and garlic behind.
To serve, plate farro, brussels and mushrooms on a serving platter. Drizzle herby vinaigrette all over and top with fresh grated parm. Enjoy!
Herby Vinaigrette:
In a small bowl, combine tarragon, parsley, lemon juice, olive oil and salt + pepper.