In a large saute pan over medium high heat, cook and crumble sausage until no longer pink. Push meat to one side of pan.
Add butter and garlic powder to sausage grease. Once fully melted add flour and tarragon and whisk together. Let cook for 3 minutes.
Whisk in heavy cream, salt and pepper. Let cook for 3 minutes then incorporate sausage back into gravy. Cook another 3 minutes then stir in milk. Let cook another 3 minutes then reduce heat to medium low.
Let simmer, stirring occasionally, for 10 minutes.