Preheat the oven to 190 C / 175 C fan oven / 375 F.
Dice the aubergine in bite sized pieces. Add it to a baking tray, and cover with 1 teaspoon oil. Sprinkle some salt, and stir to coat the aubergine pieces evenly.
Roasted the aubergine in the oven until soft, about 15 minutes.
Heat 1 teaspoon oil in a large pot. Finely dice garlic and onion, and add them to the pot. Saute until soft and translucent, about 3-5 minutes.
Add diced chicken breast to the pot, and cook while stirring occasionally until the chicken pieces are mostly white on all sides. Then, add all the spices, and leave this to saute for 2 minutes while stirring.
Add the tomato passata and roasted aubergine to the curry. Stir to combine, then leave it to cook on medium heat for about 10 minutes, or until the chicken has cooked through.
Season with salt and pepper to taste, and add more chili powder if you want the curry to be spicy.