Adjust oven rack to middle position and heat oven to 375 degrees. Microwave water and porcini in covered bowl until steaming, about 1 minute. Let sit until softened, about 5 minutes. Drain porcini through fine-mesh strainer lined with coffee filter, reserve liquid, and mince and reserve porcini.
2. Process saltines in food processor until finely ground, about 30 seconds; transfer to large bowl and reserve. Pulse 5 ounces of white mushrooms in processor until finely ground, 8 to 10 pulses.
3. Heat oil in 12-inch nonstick skillet over medium-high heat until shimmering. Add onion and cook until browned, 6 to 8 minutes. Stir in processed mushrooms and 1/4 teaspoon salt and cook until liquid evaporates and mushrooms begin to brown, about 5 minutes. Add garlic and cook until fragrant, about 30 seconds. Transfer to bowl with saltines and let cool to room temperature, about 15 minutes. Wipe out skillet with paper towels.
4. Add pork, 1/4 cup reserved porcini liquid, eggs, 1 tablespoon Worcestershire, 1 teaspoon salt, and ¾ teaspoon pepper to cooled mushroom-saltine mixture and knead gently until nearly combined. Add beef and knead until well combined. Transfer meat mixture to now-empty skillet and shape into 10 by 6-inch loaf. Bake until meatloaf registers 160 degrees, 45 to 55 minutes. Transfer meatloaf to carving board and tent loosely with aluminum foil.
5. Slice remaining 5 ounces white mushrooms. Discard any solids in skillet and pour off all but 2 tablespoons fat. Heat fat over medium-high heat until shimmering. Add sliced mushrooms and reserved porcini and cook, stirring occasionally, until deep golden brown, 6 to 8 minutes. Stir in thyme and 1/4 teaspoon salt and cook until fragrant, about 30 seconds. Add flour and cook, stirring frequently, until golden, about 2 minutes. Slowly whisk in broth, 1/2 cup reserved porcini liquid, and remaining 3/4 teaspoon Worcestershire, scraping up any browned bits, and bring to boil. Reduce heat to medium and simmer, whisking occasionally, until thickened, 10 to 15 minutes. Season with salt and pepper to taste. Slice meatloaf and serve with gravy.
**Swanson Certified Organic Free Range Chicken Broth is our ATK taste-test winner.