Equipment: 1 x 24-centimeter springform pan
1. Preheat the oven to 200°C/400°F/Gasmark6.
2. Peel and cut the onion into wedges. Cut the pear in half, take out the core, leave peel on and cut into slim wedges. Take the rosemary leaves off the stem.
3. Sauté all the ingredients and the pepper in butter for 5 minutes on a medium heat, season with salt.
4. Butter the springform pan. Take the puff pastry and place it in the pan, make sure it is even on the sides. Brush with the beaten egg, incl. the sides.
5. Place the onion-pear mix inside your pastry and divide it evenly, place in the oven and bake for 25 minutes.
6. When the tart comes out of the oven, slice your Castello creamy white and place evenly on the top, so it will gently melt into the warm tart. Take out of the springform pan and serve right away.