Preparation:
1. Preheat your oven to 180°C (350°F). Generously butter and flour a springform pan (ideally with high sides and a removable bottom for easy unmolding).
2. Prepare the fruit: peel and core all the apples. Cut half the apples into large cubes (they will melt inside the flan) and the other half into nice, even slices (for decorating the top).
3. In a large bowl, crack the eggs and whisk them vigorously with the granulated sugar and vanilla sugar until the mixture is pale and slightly frothy.
4. Add the plain yogurt and mix well. Then stir in the cooled, melted butter.
5. Sift in the flour and baking powder, and gently mix with a spatula or whisk until you have a perfectly smooth, lump-free batter.
6. Gently fold the apple cubes into the batter to coat them completely.
7. Pour the mixture into your prepared pan and smooth the surface. Then arrange the apple slices in a rosette pattern on top, packing them tightly. 8. Generously sprinkle the surface with brown sugar to achieve a beautiful golden color when baked.
9. Bake for approximately 40 to 45 minutes. The flan should be golden brown. Let it cool slightly before unmolding.
10. To achieve the ultra-glossy finish shown in the photo, worthy of a pastry shop window, heat a spoonful of jam with a drop of water and brush it over the top of your flan. Let it cool completely before enjoying!
