For the grilled corn-on-the-cob, drizzle the corn cob pieces in olive oil and season with salt and freshly ground black pepper. Heat a griddle pan until hot and griddle the corn for 4-5 minutes. Add the spring onions and griddle until chargrilled on all sides. Remove from the pan and place into a small gratin dish.
For the gratin, place the white wine, egg yolks and cream into a bowl set over a pan of gently simmering water and whisk constantly until the mixture begins to thicken.
Remove from the heat and pour the sauce over the chargrilled vegetables in the dish. Sprinkle over the cayenne pepper and crabmeat, then glaze the top with a mini-blowtorch until golden-brown and bubbling. Serve immediately.