I found several eggplant dishes, but I don't know which would be more Bulgarian. And I hate eggplants, so I can't tell you which is tastier. But if any of these interest you, I'll translate it:
1. Eggplants stuffed with cheese and baked
2. Baked eggplants with bechamel sauce
3. Sliced baked eggplants
4. Mashed baked eggplants
5. Cut in long pieces and baked eggplants
6. Eggplant moussaka
7. Oriental eggplants
8. Imambayalduh
9. Fried eggplants with yogurt
10. Eggplants with tomato sauce
11. Fried eggplants with rice
12. Eggplants fried in eggs and bread (don't know the word for that)
13. Eggplant schnitzels (three types)
14. Eggplant kyufteta
with meat:
15. Mutton with eggplants
16. Stuffed eggplants

If I have to choose, I'd say 1 and 9 are the most Bulgarian. 8 is definitely Turkish, and the name means "the imam fainted (with delight)"