01 - Preheat the oven to 400°F. Line a baking sheet with parchment paper.
02 - In a skillet over medium heat, cook the chopped bacon until crisp. Remove and set aside, leaving a little bacon fat in the pan.
03 - Add the onion to the skillet and sauté for 2-3 minutes until softened. Add the garlic and cook for 30 seconds more.
04 - Add the ground beef, salt, and pepper. Cook until browned and crumbly, breaking it up with a spatula. Drain excess fat.
05 - Stir in ketchup, mustard, and the cooked bacon. Remove from heat and let cool for 5 minutes.
06 - Unroll the puff pastry sheet on a lightly floured surface. Evenly spread the beef mixture over the pastry, leaving a ½ inch border on all sides. Sprinkle shredded cheddar on top.
07 - Starting from one long side, roll up the pastry tightly into a log. Pinch the seam to seal.
08 - Slice the roll into 16 even pieces. Place each slice, cut side up, on the prepared baking sheet.
09 - Beat the egg with 1 tbsp water to make an egg wash. Brush the tops of the rollups.
10 - Bake for 18-22 minutes, or until puffed and golden brown. Let cool for a few minutes before serving.