In a large, dry skillet, break up sausage over medium high heat, allowing fat to render - about 3 minutes. Leave sausage a decent size - 1 inch pieces are perfect.
Add chopped onion to skillet and stir to coat with fat. Allow to cook for a few minutes.
If necessary, drain excess fat from skillet. Sprinkle uncooked rice over sausage and onions and combine. Allow to cook for about 2 more minutes until well coated.
Add 4 1/2 cups room temperature water to skillet. Sprinkle in soup base, and bring entire mixture to a boil over medium high heat.
Turn heat to low and cover skillet. Allow to cook until rice is desired tenderness, about 15 minutes. Remove from heat.
Sprinkle frozen peas on top of rice and dot with butter. Replace lid and allow to sit for two to three minutes.