Q.Silver Birch pruning/topping
I have 2 large silver birch trees near my barn and 5 years ago a couple of farmer friends cut the tops off, as they were higher than the barn and my wife was worried about them falling in heavy winds. Now they have grown back very tall again and I was wondering how to trim them this time. Should I cut each large vertical branch just above where the last cut was or is there a better way?
Regards,
Dave

Unfortunately once a tree has been topped, it is difficult to improve the shape. Topping results in a weakened tree and can even accelerate the growth.
An Arborist may be able to help you with correcting prune cuts.
If the trees are in close proximity and the danger is that they could cause damage to your barn, this may be time to remove the trees.
Topped trees are susceptible to disease and can become weakened.
The articles below have more information.
https://www.gardeningknowhow.com/ornamental/trees/tgen/tree-topping-information.htm
https://www.gardeningknowhow.com/ornamental/trees/birch/cutting-back-birch-trees.htm