Preheat the oven to 400°F and generously coat a 9-inch glass pie plate with cooking spray.
Combine Bisquick mix and softened butter in a medium bowl until well mixed to create a crumbly mixture. Then, add hot water and stir until a soft dough forms. Press the dough into the bottom and up the sides of a pie plate.
Create a savory assembly by arranging cheese, sausage, and green onions over the crust in a pie plate. In a separate medium bowl, whisk together half-and-half, Cajun seasoning, and eggs until well combined. Carefully pour the mixture over the prepared pie plate.
Bake for 32 to 38 minutes until a knife inserted in the center comes out clean. Allow to stand for 10 minutes before serving.