Preparation
Preheat the oven to 200°C, fan 180°C, gas 6. Melt the butter and brush about half over a roasting tin measuring about 25cm x 35cm. Lay 4 tortillas into the tin so that they overlap and cover the base and sides completely, with the edges coming up above the tin to fold in later. Scatter the cheese all over the base.
Tear the chicken into bite-sized pieces. Rinse and drain the black beans and add to a bowl with the chicken, some seasoning and the cumin for earthiness. Finely chop the red onion and coriander and stir some of each through half a pot of salsa, then set this aside in a small bowl to serve. Mix the rest of the red onion and coriander through the chicken mixture then scatter evenly over the cheese. Spoon on the rest of the salsa, a handful of jalapeño slices for kick and dollop on the soured cream for richness.
Lay the other 2 tortillas on top, then brush with the rest of the melted butter, folding in the tortilla edges to encase the filling. Mark into 12 squares with a serrated knife then bake for 20 minutes or until piping hot, golden brown and crisp.
Leave to rest for 5-10 minutes to cool slightly. Scatter with extra coriander and serve with the reserved salsa and the guacamole.