I didn’t know. I think these might help.
The gist of all those ideas is have the cookie dough flatten out as they bake so the dry and brown better. I wonder if Huel black would bake differently with higher protein compared to carbs. Lower temp, longer time might help dry the cookie more. Also, darker cookie sheet can help them brown more. Have you tried butter instead of the coconut oil? Yeah, definitely not vegan but that might not be your concern?