Step 1Make the tomato sauce: Spray a medium saucepan with olive oil and set over medium heat. Sauté onion for 8 minutes, or until soft. Add garlic and cook for 2 minutes. Add the passata and spice mix; reduce heat to low and simmer for 15 minutes, or until reduced by a third. Add the chillies, season with cracked black pepper and remove pan from heat.
Step 2Meanwhile, heat a large chargrill pan over a high heat. Spray the onion wedges, capsicum and the chicken with olive oil. Cook in batches for 3–4 minutes on each side, or until vegies are tender and the chicken is cooked through. Set aside on a plate.
Step 3Heat tortillas, one at a time, on the same pan for 10–20 seconds each side, or until warm. Transfer the tortillas to a plate. Cover with a clean tea towel to keep them soft.
Step 4Preheat the oven to 180°C. Make the béchamel sauce: Heat the olive oil in a medium saucepan over medium heat, then beat in the flour vigorously with a whisk to form a smooth paste. Remove the pan from the heat, then slowly whisk in the hot chicken stock, bit by bit. When it is all incorporated, repeat with the yoghurt, whisking until smooth and thick enough to coat the back of a spoon.
Step 5To assemble the enchiladas, spread 1 tablespoon of the tomato sauce over the middle of each tortilla and spoon a line of beans down the centre. Divide the chicken and the vegetables among them. Fold over to enclose the fillings, then put the tortillas on a lightly oiled baking dish, seam-side down.
Step 6Pour the remaining tomato sauce over the tortillas, then the béchamel. Sprinkle with grated cheese and bake enchiladas for 15–18 minutes, or until bubbling. Garnish with coriander and serve with mixed salad leaves.