Use a medium saucepan and add broth and butter to it. Heat on high until your liquid begins to boil. Then, remove the saucepan from heat.
Combine milk and cornstarch in a small bowl.
Mix the cornstarch into your broth while the broth is hot. Mix together well.
Boil the mixture on high until it starts to simmer. Then, add in garlic powder, poultry seasoning and pepper.
Taste the gravy and add salt as necessary.