Making your Apple Danish is as simple as following these steps:

1. Prepare the Apples: In a medium saucepan over medium heat, melt the butter. Add the diced apples, sugar, cinnamon, and lemon juice. Cook for 5-7 minutes or until apples begin to soften. Remove from heat and let cool.

2. Preheat Oven: While the apples cool, preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper.

3. Prepare Puff Pastry: On a lightly floured surface, roll out each puff pastry sheet into a rectangle, roughly 12×8 inches. Cut each sheet into four equal squares.

4. Fill the Pastry: Place 2 tablespoons of the cooled apple filling in the center of each square. Be careful not to overfill.

5. Fold and Seal: Fold opposite corners of each pastry square towards the center to form a diamond shape, pinching the edges together to seal. Alternatively, you can twist them for a decorative touch.

6. Apply Egg Wash: Brush the tops of each Apple Danish with the beaten egg. This will give them a lovely golden color when baked.

7. Bake: Place the pastries on your prepared baking sheet and bake for 25-30 minutes, or until golden brown and flaky. Remove from the oven and allow cooling for about 10-15 minutes.