In a large skillet over medium heat, cook the breakfast sausage, breaking it up with a spoon, until fully browned and cooked through, about 5-7 minutes. Drain any excess grease and set aside to cool slightly.

In a medium bowl, whisk the 3 large eggs with 2 tablespoons of milk, salt, and pepper until well combined.

In the same skillet (or a clean one), pour the egg mixture. Scramble the eggs over medium-low heat until just set but still moist, about 2-3 minutes. Do not overcook.

In a bowl, combine the cooked sausage, scrambled eggs, and shredded cheddar cheese. Mix well and let cool completely before assembling the pop-tarts. This prevents the pastry from getting soggy.

Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper.

Lightly flour a clean surface. Unroll one sheet of pie crust (or puff pastry). If using pie crust, you might need to roll it out slightly thinner to about 1/8-inch thickness. If using puff pastry, unfold it. Cut the pastry into 4 equal rectangles (about 3x4 inches each). Repeat with the second sheet of pastry, so you have 8 rectangles in total.

Spoon about 2-3 tablespoons of the cooled savory filling onto the center of 4 of the pastry rectangles, leaving a border around the edges.

Place the remaining 4 pastry rectangles over the top of the filled rectangles, aligning the edges.

Gently press down around the edges to seal. Use a fork to crimp the edges firmly, ensuring no filling will leak out during baking. Cut 2-3 small slits on the top of each pop-tart to allow steam to escape.

In a small bowl, whisk the remaining large egg with 1 tablespoon of water (or milk) for the egg wash.

Brush the tops of the assembled pop-tarts with the egg wash.

Carefully transfer the pop-tarts to the prepared baking sheet.

Bake for 18-22 minutes, or until the pastry is golden brown and puffed.

Remove from the oven and let cool on the baking sheet for a few minutes before serving. They are best enjoyed warm.