Preheat your oven to 400°F (200°C).
In a large mixing bowl, combine the ground beef, breadcrumbs, Parmesan cheese, parsley, egg, minced garlic, salt, and pepper. Mix until well combined.
Form the mixture into meatballs (about 1.5 inches in diameter) and place them on a baking sheet.
Bake the meatballs in the preheated oven for 15-20 minutes or until browned and cooked through.
While the meatballs are baking, prepare the gravy. In a large skillet, heat olive oil over medium heat. Add the chopped onion and cook until translucent, about 5 minutes.
Stir in the flour and cook for another minute to create a roux. Slowly whisk in the beef broth and soy sauce, stirring until the mixture thickens. Add dried thyme and season with salt and pepper.
For the cauliflower mash, chop the cauliflower into florets and steam until fork-tender, about 10 minutes.
In a medium saucepan, combine the steamed cauliflower with heavy cream, butter, salt, and pepper. Mash with a potato masher or blend with an immersion blender until smooth.
Serve the meatballs on a bed of creamy cauliflower mash, topped with the gravy.