Preheat your oven to 350 degrees F.

Coat the inside of a 9-inch by 13-inch baking dish with non-stick cooking spray.

Bring a large pot of water to a boil. Add the egg noodles and cook them for 8 minutes until they are al dente. Drain the noodles and set them aside to cool.

While the noodles cook, place a skillet over medium heat. Add the olive oil, and once it's hot, add the diced onions. Cook the onions until they are soft and translucent, about 5 minutes. Add the minced garlic and cook for an additional 30 seconds until fragrant.

In a large mixing bowl, add the cream of chicken soup and cream of mushroom soup. Pour in the milk and chicken broth, then whisk until well combined and smooth.

Add the cooked chicken, noodles, mixed vegetables, and sautéed onions to the soup mixture. Stir everything together until evenly combined.

Pour the mixture into the prepared baking dish, spreading it into an even layer.

Bake for 25 minutes until the casserole is bubbling and the top is starting to turn golden brown.

Remove the casserole from the oven and sprinkle chopped parsley over the top for freshness. Serve warm.