Preparation Steps

• Preheat oven to 350°F (175°C). Grease a 9x13-inch baking dish.
• Brown the breakfast sausage in a skillet over medium heat, breaking into crumbles until no pink remains. Drain excess fat and set sausage aside.
• If using onion, sauté chopped onion in butter in the skillet over medium heat until translucent, about 5 minutes. Add onion to the cooked sausage.
• Make the gravy: return skillet to medium heat, sprinkle flour over any remaining fat, and cook 1 to 2 minutes while stirring. Gradually whisk in 2 cups of milk until smooth and thickened. Season with 0.5 teaspoon salt and 0.25 teaspoon pepper. If gravy is too thick, add additional milk to reach desired consistency.
• Tear biscuits into bite-sized pieces and spread evenly in the prepared baking dish. Sprinkle half of the shredded cheddar over the biscuit pieces.
• Scatter the cooked sausage and onion mixture evenly over the biscuits. Pour the gravy over the top, distributing evenly.
• In a bowl, whisk together the remaining 0.5 cup milk, the eggs, remaining salt, pepper and sage. Pour the egg mixture over the casserole, pressing gently so biscuits absorb the custard. Top with remaining cheddar cheese.
• Bake uncovered for 40 to 45 minutes, or until the top is golden and eggs are set. Let rest 5 to 10 minutes before serving.