Finally tried the burger, after reading all of the rave reviews!
It's... ok, but I'm not inclined to return.
The medium rare doness and beet chutney are what make it memorable: juicy meat and a nice acidic kick. Otherwise, the flavour of the burger patty itself wasn't very memorable. It looked a bit small too, but after finishing the plate with fries I was surprisingly full.
Speaking of fries, I couldn't taste the rosemary: tasted regular.
Nothing special going on with the bun either.
All in all a decent meal.
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The decor and atmosphere are decent.
Service was fine.