Medlar cake - my own recipe

Ingredients: for 15x22 cm oven

For the dough:
50 g unsweetened cocoa
50 g all-porpouse flour
70 g powdered sugar
2 egg yolks
50 g unsalted butter
2 tbsp sour cream
pinch of salt
1 tsp rum (optional)
few drops of vanilla extract

For the filling:
0,5 kg medlar
1 tbsp cornstarch
1 tbsp honey

For the top:
2 egg whites
40 g powdered sugar
few drops of vinegar (or lemonjuice)

Preparation:

1. Wash the medlars and cook them in water until soft.
2. Pour off the water. Make puree with a strainer from medlars. Let it cool.
3. Add the starch and honey to the puree. Mix them.
4. Preheat the oven to 180 Celsius (340 F).
5. Mix flour, cocoa and salt in a bowl.
6. Beat egg yolks, sugar and soft butter with the mixer.
7. Add the dry ingredients to the mixture.
8. Add sour cream, vanilla, rum too and stir them well. This dough will be thick and creamy.
9. Spread the dough in the pan.
10. Spread the medlar puree on the top of the dough.
11. Bake the cake for 15 minutes.
12. While the dough is baking beat hard foam from the egg-whites, add the vinegar and sugar. Beat them very well.
13. Pull the dough out of the oven. Spread the foam on the top of the dough. Make a nice pattern on the top of the foam with a fork.
14. Bake it in the oven for another 5-7 minutes.
15. Let it cool and cut 5x5 cm (2x2 inch) cubes.