How do you forge this detail?

[Ice Czar]

we do quite a bit of that kind of welding at the shop, and generally the issue is getting enough penetration, without having to do a lot of cleanup grinding

which is where plug welding one of the bars is so useful, the hole your filling gets great penetration to a thick stock where otherwise your just getting parameter penetration, then you can just do a light weld around the outside without having to worry about how well it holds. of course joining the bar to the other side generally entails a fairly serious bevel to fill to ensure penetration.

Actually forging the detail by upsetting then freehand shaping or swagging is going to be substantially stronger, more resilient and less brittle than any weld. But then welding and grinding would be much faster if the resiliency and strength aren't required.