Preheat an oven to 375°F. Butter a 13x9-inch casserole dish and set aside.
Heat a 12-inch, nonstick skillet over medium-low heat. Add the sausage, breaking it up with a kitchen spoon as it cooks. Once the sausage fat starts to render out and the sausage is completely cooked, about 12 minutes. Remove the sausage to a paper towel-lined plate to drain. Place the empty pan back over the heat.