Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper to prevent sticking without using oil.
Scrub the sweet potato and cut it into 1-inch cubes, then spread them in a single layer on one half of the prepared baking sheet.
Finely mince the portobello mushroom, celery stalk, and garlic clove until they are uniform, very small pieces.
In a large mixing bowl, combine the minced top side beef with the egg white, sea salt, cumin powder, and paprika.
Fold the minced mushroom, celery, and garlic into the beef mixture, mixing gently by hand until just combined.
Roll the mixture into 1.5-inch meatballs and arrange them on the other half of the baking sheet.
Bake for 20 to 25 minutes until the meatballs are cooked through and the sweet potato cubes are tender and lightly browned.
While the meatballs bake, steam the broccoli florets for 5 minutes until they are vibrant green and tender-crisp.