Preheat your oven to 350°F (175°C).
Open the canned chicken and drain any excess liquid.
In a large mixing bowl, combine the chicken, diced vegetables, mayonnaise, and mustard.
Add garlic powder, salt, and pepper to the mixture.
Mix until all ingredients are well-combined.
Transfer the mixture into a baking dish.
If using, sprinkle shredded cheese on top of the chicken mixture.
Bake in the preheated oven for 20 minutes or until heated through.
Remove from the oven and let it cool for a few minutes.
Garnish with fresh herbs before serving.