The only time a cross cut in the bottom of a sprout's stem is when we are cooking a batch of various sizes. On these occasions, cut a cross in the larger sprouts. This allows heat to penetrate more easily to the middle so that the larger sprouts cook in the same time as the smaller ones.
Brussels sprouts are at their best when they are very tight, small buds and, since most supermarkets now sell them in a fairly regular and quite small size, crosscutting the stalks is rarely necessary.
** Asian Online Recipes