Best quality wood worktop sealant

Morning all.

I fitted our own kitchen a couple of years ago. We spent a small fortune on solid oak worktops and then I (cleverly) used a cheap silicone sealant between the worktop and upstand. The result is shown in the photo.
View attachment 85513

What would the pro kitchen fitters up here recommend, to replace it? Something that won’t shrink away like this.

Thanks in anticipation.
Jez