For the paste, place the macadamias and sugar in the bowl of a food processor and process until fine. Add the egg white and process to combine. Set aside.
Preheat oven to 180C. Lay the apple halves flat on a surface and slice as thinly as possible. If you have a mandolin, use this to slice the apples.
Place the apples in a microwave proof bowl and dot with butter. Sprinkle with sugar, lemon juice and water and gently fold to combine. Microwave on high for 30 seconds, until apples are just tender. Alternatively place in a saucepan with the butter, sugar, lemon juice and water and simmer for 3-4 minutes, until just tender. Remove the slices from the bowl and place on a paper towel to remove excess moisture.
Roll the puff pastry out as thinly as possible and cut crosswise into thick strips approx. 4cm x 25cm. Spread 2 teaspoons of macadamia paste across the middle of each strip. Place individual apple slices rounded side up and slightly overlapping along the top edge of each strip. Fold the bottom edge up toward the top, encasing the bottom of the apple slices. Start from one end and roll the dough into a coil, creating ‘roses’. Press the end to seal.
Place individual roses into the holes of a muffin tin and cook for 15-20 minutes, until the pastry is puffed and the apples are just turning golden.
Serve sprinkled with icing sugar.
Any leftovers can be stored in an airtight container.