You could serve this as a starter for a dinner party or as a light lunch snack. If you live by the sea you will have access to various types of sea vegetables, or you can even buy sea aster these days from branches of Waitrose.
A handful or so of sea vegetables (sea aster, sea beet, sea purslane etc)
A couple of knobs of butter
100-120g freshly picked white crab
2-3tbsp brown crab meat (optional), mixed with a tablespoon of mayonnaise
Salt and freshly ground white pepper
1tbsp olive oil
Toast the crumpets on both sides. Melt the butter in a pan and gently cook the sea vegetables for about a minute until they have just wilted. If using, spoon the brown crab on to the crumpets, then arrange the white crab and sea vegetables on top and lightly season. Spoon a little olive oil over and serve.