Steadily but not at a gallop

So before I enter into this Elizabeth David malarkey I figured I should try out a recipe or two. I started with a soup, simple, Potage Bonne Femme.
Melt some butter in a pan, add the finely sliced 2 leeks* and 3 diced carrots. "Let them get thoroughly hot and saturated with the butter", add 1lb of potatoes diced, 2 and a bit more pints of water, salt and tsp of sugar. "Cook steadily but not as a gallop" (fave line so far. Sieve through a mouli, I have a personal fear of sieves or moulis, but the result was worth it. Add a bit of cream and parsley.
Delicous good first attempt, well done. Pleased not to rely on bouillon and for the flavor to be better without.
*revolutionary new way of washing leeks, remove outer leaves, cut off root end and cut cross in bottom, run under cold tap, then rest cut side down in jug of cold water whilst preparing other veg(or 30 mins), result=clean leeks.