Preheat your oven to 350°F.
Grease the 9x13 inch baking dish thoroughly.
Cook sausage in skillet until browned completely.
Drain excess fat from cooked sausage.
Mix pancake mix, milk, and eggs together.
Add melted butter and vanilla to mixture.
Pour half the batter into prepared dish.
Sprinkle cooked sausage over the batter evenly.
Add remaining batter on top carefully.
Drizzle maple syrup over the entire casserole.
Top with shredded cheddar cheese generously.
Cover with foil and bake 25 minutes.
Remove foil and bake 10 more minutes.
Let cool for 5 minutes before serving.