In a medium bowl, combine the torn bread and milk. Press the bread into the milk until it’s fully soaked and soft. Let it rest for about 5 minutes.

In a large mixing bowl, add ground beef, salt, pepper, garlic powder, onion powder, parsley, beef bouillon, mushroom powder (if using), ketchup, Dijon mustard, Worcestershire sauce, and the egg. Pour the soaked bread mixture (including leftover milk) into the bowl. Gently mix everything by hand or with a spatula until just combined.

Scoop about 3 tablespoons of mixture for each meatball. Roll into 2-inch balls with damp hands to prevent sticking. Set them aside on a plate while preparing the sauce.

In a skillet over medium heat, add a drizzle of oil and lightly brown the meatballs on all sides (about 2–3 minutes per side). Transfer the browned meatballs into your slow cooker. In the same skillet, add sliced mushrooms and shallots. Sauté for about 3 minutes until softened. Stir in tomato paste, smoked paprika, thyme, rosemary, soy sauce, and brown sugar. Cook for 1 minute, scraping any browned bits from the pan. Pour in the beef broth and bring to a gentle simmer for 2 minutes. Then pour this mixture over the meatballs in the slow cooker.

Cover with the lid and cook on Low for 4 to 5 hours, or until the meatballs reach an internal temperature of 165°F.

When done, gently remove the meatballs and set them aside. If your slow cooker insert can be used on the stovetop, place it over medium heat; otherwise, transfer the liquid to a saucepan. Add the optional browning sauce for a richer color and bring the liquid to a boil. In a small bowl, whisk together cornstarch and heavy cream until smooth. Slowly pour this slurry into the boiling sauce while whisking constantly. Continue cooking for 5–6 minutes, until the gravy thickens enough to coat the back of a spoon.

Return the meatballs to the thickened gravy and stir gently to coat. Taste and adjust seasoning with salt or pepper as needed. Serve warm over mashed potatoes, egg noodles, or steamed rice.