1) Preheat the oven to 180C/Gas 4.
2) Heat the extra-virgin olive oil in small frying pan over medium-high heat. Dice the Spanish chorizo and add to the pan to render the fat. If using fresh Mexican chorizo, remove the casing and crumble while it's browning. Add the mushrooms to the frying pan and cook with the sausage until just tender, 6 to 7 mins. Transfer the sausage mixture to a small casserole or baking dish and top with the cheese.
3) Bake until bubbly. Remove from the oven and top with the spring onions.
4) Serve with crisps for dipping.