Preheat the oven to 400°F (200°C).
In a large mixing bowl, combine the ground beef, breadcrumbs, Parmesan cheese, parsley, egg, garlic, salt, black pepper, and onion powder. Mix until just 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 20 minutes or until cooked through and browned.
While the meatballs are baking, make the gravy. In a large skillet, melt the butter over medium heat. Stir in the flour and cook for 1-2 minutes until lightly browned.
Gradually whisk in the beef broth, then add the Worcestershire sauce. Bring to a simmer and let it thicken, stirring occasionally. Season with salt and pepper to taste.
For the cauliflower mash, steam the chopped cauliflower until tender, about 10 minutes. Drain and place in a bowl or food processor.
Add the heavy cream, butter, salt, and pepper to the cauliflower and mash until smooth and creamy. Adjust seasoning as needed.
To serve, place a generous scoop of the creamy cauliflower mash on each plate, top with meatballs, and drizzle with gravy. Garnish with chopped chives or parsley if desired.