Good to know! I wasn't sure how much to whack off... I really want a large shrub, not a tall tree, so I will try your method. I assume I should do that when it's dormant?

If it isn’t fully leafed out do it now. Or really whenever since they tend to be forgiving.

Needs to be done early in the year - such as right after bloom - or the top may not come back fully before the end of summer. Also in that shaded position it may not grow as strongly as a specimen located in full sun.

Thanks, Embo. Mine is in full sun, so regrew uneventfully.

You can't really kill it unless you try! Had them for years and they can take a heavy pruning no problem. If you do it now, you will be fine and have the catkins next spring. You could even hold off until June, but no later. Looking at the photo, you could prune it to a small tree form now if you would like that. Then every year after it's done blooming, cut it back to the top of the trunk (they call this "pollarding" and it's done a lot in Europe). On the other hand you could cut it back to a foot or so and have it as a bushy plant.

You can do the "pollard" method each year by cutting the sing;e largest trunk to a convenient height, typically around 4 feet for a willow. The new growth (4-6 feet by season's end) will come from there each year. In spring when the catkins are at that pretty fuzzy stage is when most people harvest the stalks and let them dry to use for decoration indoors. At that point you're left with the 4 foot trunk, with several stubs of the cur branches, and the cycle repeats. My plants done like this usually give me a couple of dozen or more cut stalks about 4-6 feet long. And the 4 foot height trunk makes it easy to prune/harvest.