Heat 1 tablespoon olive oil in a large, deep frying pan or casserole over medium-high heat. Add the chicken mince, season generously with salt and pepper and cook for 7–8 minutes.
Add the corn and red capsicum, cook for a few minutes until beginning to soften slightly.
Add the cumin, smoked paprika and coriander. Cook for about 30 seconds, then add the chipotle and tomato paste. Cook for another 1–2 minutes, stirring, until the tomato paste darkens slightly.
Add the crushed tomatoes, 200ml chicken stock and grated zucchini. Bring to a simmer and cook uncovered for approximately 15 minutes, stirring occasionally, until the vegetables have softened into the sauce.
Stir in the spinach and cook until wilted. Add the black beans and simmer for another 5 minutes.
Stir through the lime juice and check the seasoning. The finished filling should be quite saucy rather than thick and dry. If necessary, add some or all of the remaining 100ml stock.
Heat a frying pan over medium-high heat. Brush the corn tortillas very lightly with olive oil and cook for approximately 15–20 seconds on each side. You only want them pliable with a few lightly toasted spots; don’t cook them until crisp.
Lightly oil a large baking dish, approximately 23 x 33cm. Spread a generous layer of chicken and black bean filling over the base.
Cover with a single layer of tortillas, cutting them where necessary to fit. Add the remaining chilli mixture and cover with another single layer of tortillas.
Spread a thin layer of mild salsa over the top tortillas. You want enough to cover and moisten them without creating a thick salsa layer. Scatter over the cheese if using.
Bake at 190°C conventional / 170°C fan-forced for approximately 25–30 minutes, until the filling is bubbling and the cheese is lightly browned.