Start water boiling for potatoes. Once at a rolling boil, add quartered potatoes. Salt water, if desired. Cook until fork tender.
In a large saute pan over medium-high heat, add sausages and roll around until all sides are browned. Reduce heat to medium and add half cup of broth. Cover and let cook for 10 minutes more.
In a medium sauce pan over medium heat, add 3 tablespoons of butter, salt and pepper. Once melted add frozen peas. Stir and toss to coat. Reduce heat to medium low and cover. Let cook until ready to serve.
Remove sausages from pan and keep warm. Add butter. Once melted, add garlic, onions, salt and thyme to same pan. Let saute for 3 minutes. Add cornstarch, stir together and let cook another 3 minutes. Whisk in pepper and broth. Continue to cook until thickened. Reduce heat to low and let simmer while you prepare the rest of the meal.
Drain potatoes in colander and place in large mixing bowl. Add melted butter, salt, white pepper and heavy cream. Smash and mix potatoes to desired consistency (I like to leave them a little chunky)
In a shallow bowl, add a portion of potatoes, 1-2 sausage, a portion of peas and then ladle on onion gravy.