Sweet chickpea tagine

How much this constitutes a tagine I’m not sure given how many ingredients I substituted from the original recipe, which was for a fish tagine. Serves 3 with bulgar wheat or naan, or 2 alone; reheats well the next day.

Melt ~1 tbsp butter in a heavy bottomed saucepan and caramelise 3-4 stalks celery, diced, and 3 cloves garlic, finely chopped. Add 1 tsp curry powder, 1 tsp garam masala, 1 tsp turmeric, 1/2 tsp cumin seeds, 1/2 tsp coriander seeds, 1/2 tsp ground ginger and a pinch of chilli flakes to taste, coating the celery and garlic thoroughly. Add 1/2 plantain, 1 apple, 1/2 courgette and 1/2 mango, all diced into 1 cm cubes and cook, stirring continuously, until the pan begins to smoke. Add 1 400g can chopped tomatoes, 1/2 can water and 1 tsp stock powder. Bring to the boil, then reduce to a low heat, cover, and leave for 20-30 minutes, stirring occasionally, until most of the liquid has reduced. If the tagine is still a little sour, add 1 tsp brown sugar. Stir in 1 400g can chickpeas and cook for another 5 minutes, then serve.