Cut out some rounds of bread a good deal larger than a poached egg would be. While these are frying, make a puree of Brussels sprouts. Boil them till tender, squeeze in a cloth. Rub them through a sieve and make into a very thick puree with cream, pepper and salt. Poach a fresh egg for each crouton, and slip it on, very quickly, put some of the green puree round, and serve under a hot cover.