To make the guacamole, mash the avocados and stir together with the lime juice, chilli and garlic. Season to taste and set aside.
Heat the oil in a large, lidded pan over a high heat and cook the onion and peppers, uncovered, for 5 minutes. Add the mushrooms, stir together well, turn the heat down a little, put on the lid and cook for 5 minutes. Remove the lid, turn the heat back up and cook, stirring, for 5-6 more minutes, to evaporate some of the liquid. Stir in the tomato purée, Mexican seasoning and Tabasco. Stir well and cook for a minute more to create a sauce.
Divide the mushrooms and a little sauce between each of the tortillas, top with some soured cream, guacamole and a handful of coriander. Roll up and serve.