what were your baking parameters ?
were the potatoes previously cooked ?
?they look nicely browned
P.S.: try just a little freshly grated nutmeg in the béchamel,
or for that matter anything ' white ' ie mashed potatoes
if you already haven't tried this. just a little . not enough to notice ' nutmeg '
I always try to remember this w potatoes , and béchamel back in the day.