In a large ovenproof, nonstick skillet, heat olive oil over medium, and cook onion until softened and just beginning to brown, about 3 minutes.
Add vegetables and garlic powder to skillet and cook until thawed, about 2 minutes.
Sprinkle flour over onion and vegetables. Toss to coat and cook another 2 minutes.
Add broth, almond milk, chicken, salt and pepper; stir and bring to a boil. Reduce heat to low and cook until thickened, stirring occasionally, 15 minutes. Preheat broiler.
Remove from heat, smooth top and sprinkle with breadcrumbs. Place under oven broiler until breadcrumbs are browned, about 1 minute.