1. Make the Sausage Gravy:

• Place a large skillet over medium-high heat. Add the ground sausage to the skillet.
• Cook the sausage, breaking it up into smaller crumbles with a spoon or spatula, until it is completely browned and cooked through.
• Drain Fat (Optional but Recommended): Tilt the skillet and carefully spoon out most of the excess rendered fat, leaving about 3-4 tablespoons of fat in the skillet (this will be used to make the roux). If your sausage was very lean, you might need to add a tablespoon or two of butter here to have enough fat.
• Sprinkle the 1/4 cup of all-purpose flour evenly over the cooked sausage and remaining fat in the skillet. Stir it in well and cook, stirring constantly, for about 1-2 minutes to cook out the raw flour taste.
• Gradually pour in the 2 cups of milk while stirring or whisking constantly to prevent lumps from forming.
• Increase the heat slightly to bring the mixture to a gentle boil, stirring frequently. Once it bubbles, reduce the heat to low and let it simmer, stirring often, until the gravy thickens nicely, about 5 minutes.
• Stir in the salt (start with less, taste after simmering), black pepper, ground sage, and optional crushed red pepper flakes. Taste and adjust seasonings as needed. Remove the gravy from the heat and let it cool slightly while you prepare the pastry.

2. Prepare Oven and Pie Dish:

• Preheat your oven to 375°F (190°C).
• Have your 9-inch pie dish ready.

3. Assemble the Pie:

• Ensure your puff pastry is properly thawed but still cool. Gently unfold one sheet of puff pastry. If needed, lightly roll it out on a floured surface just enough so it will fit into your 9-inch pie dish with some overhang.
• Carefully place the first sheet of puff pastry into the pie dish, pressing it gently into the bottom and up the sides. Allow the excess pastry to hang over the edges for now.
• Pour the prepared (slightly cooled) sausage gravy into the pastry-lined dish, spreading it out evenly.
• Gently unfold the second sheet of puff pastry. Place it carefully over the top of the sausage gravy filling.
• Trim and Seal: Trim the excess pastry from both the top and bottom crusts, leaving about a 1/2-inch overhang around the rim of the pie dish. Fold the top edge under the bottom edge and press together firmly to seal. Crimp the edges decoratively with your fingers or a fork.
• Vent: Cut a few small slits (about 3-4) in the center of the top crust using a sharp knife. This allows steam to escape during baking.

4. Bake:

• Place the assembled pie on the middle rack of your preheated oven. (Placing it on a baking sheet can help catch any potential drips).
• Bake for 25-30 minutes, or until the puff pastry is beautifully golden brown, puffed, and flaky.

5. Cool Slightly and Serve:

• Carefully remove the pie from the oven.
• Let the Sausage Gravy Puff Pie cool in the dish on a wire rack for at least 10-15 minutes before slicing. This allows the hot gravy filling to set slightly.
• Slice into wedges and serve warm. Enjoy the hearty layers!