In a medium bowl, whisk together 1 cup of vegetable broth, 3 tablespoons of soy sauce, 1 tablespoon of brown sugar, and 1 tablespoon of sesame oil until fully combined. Set it aside as you prep and cook the vegetables.

Heat 1 tablespoon of neutral oil in a large skillet over medium heat. Add sliced carrots and sauté for about 3-4 minutes until they turn golden brown and slightly tender. Remove them from the skillet and set them aside on a plate.

In the same skillet, add another tablespoon of oil if needed and toss in chopped onions, broccoli florets, and red bell pepper slices. Sauté these vibrant veggies for 4-5 minutes until they become tender and slightly caramelized.

Return all the sautéed vegetables to the skillet. Press 3 minced garlic cloves into the mix and stir everything together over medium heat for about 1-2 minutes.

Introduce the precooked lo mein noodles to the skillet with the sautéed vegetables. Pour the sauce over the mixture and toss everything together, cooking for an additional 3-5 minutes until thoroughly heated.

Remove the skillet from the heat. Serve this colorful dish immediately in bowls and garnish with sliced green onions or sesame seeds.