I keep my sourdough starter on the kitchen counter and feed it at the same time every day, at 6:00 AM. I discard 80% of the ripe starter before feeding, just enough for two crumpets. Very convenient.
When I usually make crumpets, I mix a batter with my starter the night before and cook them off in the morning (12 hour ferment). However, since I have to discard some of my starter every day when I feed it, I like to use it when I can.
Heat a griddle and buttered egg ring over a low heat. Mix in a teaspoon of caster sugar, a pinch of salt and a bare 1/4 teaspoon of baking soda. Fill the egg ring 1/2 full and let cook slowly for about 8 minutes, until only a 2-3cm circle uncooked batter is left in the centre. Remove the ring and turn over to cook the other side for a minute or two, until lightly browned. Best when served hot from the griddle.