First, let's get the sauce ready. In a small bowl, whisk together the maple syrup, soy sauce, chili paste, cornstarch, rice vinegar, and sesame oil. Set this aside – it's going to bring everything together at the end!
Next, let's prep those veggies. Make sure your sweet potatoes are cut into roughly equal bite-sized cubes so they cook evenly. Trim and halve your Brussels sprouts. Mince your garlic and ginger. Slice those scallions, keeping the white and green parts separate.
Now, let's make the meatballs! In a medium bowl, gently combine the ground beef, panko bread crumbs, milk, kosher salt, minced garlic (use about half, save the rest for the veggies!), minced ginger (use about half), and the white parts of the sliced scallions. Don't overmix! Just combine until everything is incorporated. Roll the mixture into small, uniform meatballs, about 1-inch in size.
Heat a tablespoon of oil (use a neutral oil like vegetable or canola, or even a bit more sesame oil) in your large skillet or wok over medium-high heat. Add the sweet potato cubes and cook for about 5-7 minutes, stirring occasionally, until they start to soften and get a little color.
Add the Brussels sprouts to the pan with the sweet potatoes. Cook for another 5-7 minutes, stirring, until the sprouts are tender-crisp and slightly browned. You might need to add another tiny splash of oil if the pan looks dry.
Push the vegetables to one side of the pan. Add the remaining minced garlic and ginger to the empty space and cook for about 30 seconds until fragrant.
Now, add the meatballs to the pan, nestling them among the vegetables. Cook the meatballs, turning gently, for about 8-10 minutes, until they are browned on all sides and cooked through.
Give your prepared sauce a quick whisk (cornstarch settles!) and pour it over the meatballs and vegetables in the skillet. Stir gently to coat everything evenly.
Bring the sauce to a simmer and let it bubble for 1-2 minutes, stirring, until it thickens and creates a beautiful, glossy glaze coating the meatballs and veggies.
Remove from the heat. Garnish generously with the green parts of the sliced scallions.
Serve immediately! I love serving this over fluffy white rice or brown rice to soak up all that delicious sauce.