How would you fill this gap?

[Adam1991]

What it says in the title...

i’ve tried the thickest quadrant I can find and its still too small to cover the gap.

here i’ve got a think bit of architrave but theres quite big gaps where it meets the wall.

 

[sircerebus666]

Any chance of a better pic of the gap itself?

The angle of your current pic doesn't show it very clearly

 

[foxhole]

Wider architrave, and scribe it in.