1. Preheat the oven to 350°F (175°C). Lightly grease a 9×13-inch baking dish with the unsalted butter, making sure to coat the bottom and corners.

2. In a large skillet over medium heat, cook the breakfast sausage, breaking it apart with a spatula. When it is about halfway browned, stir in the finely chopped onion (or onion and bell pepper mix). Continue cooking until the sausage is fully browned and the vegetables are soft. Drain off any excess grease and set the mixture aside to cool slightly.

3. Open the crescent roll dough and unroll it into the prepared baking dish. Press the seams together with your fingers to form one even sheet of dough, gently stretching it so it covers the bottom of the pan from edge to edge.

4. Spread the sausage and onion mixture evenly over the crescent roll crust, making sure it is distributed in an even layer so each slice will have plenty of filling.

5. Sprinkle about 1 1/2 cups of the shredded cheddar cheese over the sausage layer, reserving the remaining 1/2 cup of cheese for the top.

6. In a large mixing bowl, whisk the eggs until the yolks and whites are completely blended. Add the whole milk and heavy cream and whisk again until the mixture is smooth.

7. Season the egg mixture with kosher salt, black pepper, garlic powder, onion powder, and smoked paprika if using. Whisk to combine so the seasonings are evenly distributed.

8. Slowly pour the seasoned egg mixture over the sausage and crescent roll layers, moving around the pan so it covers everything evenly. Gently tap the dish on the counter to help the eggs settle into all the gaps.

9. Sprinkle the remaining 1/2 cup of shredded cheddar cheese over the top of the casserole. At this point you can cover the dish tightly and refrigerate it for at least 2 hours or up to 12 hours if you want to make it ahead.

10. When you are ready to bake, remove any plastic wrap, cover the casserole loosely with foil if desired, and place it in the preheated oven. Bake for 30–40 minutes, removing the foil for the last 10 minutes, until the center is set and the top is puffed, golden, and bubbly.

11. Take the casserole out of the oven and let it rest for 10–15 minutes so it can firm up for clean slices. Garnish with chopped fresh parsley or chives, then slice and serve warm.