Cook the Angel Bay Gourmet Lamb Burger Patties according to instructions on the packet.
Make the yoghurt feta sauce. Place all the sauce ingredients in a bowl and mash with a fork (or use an immersion blender) until well combined and almost smooth. Season with salt and pepper to taste.
Peel cucumber into ribbons and finely slice the onion. Cut the burger buns in half and lightly toast or grill.
Spread the bottom halves of the buns with some of the yoghurt feta sauce. Top with lettuce, beetroot, burger patties, cucumber and onion. Spread yoghurt sauce on the top halves of the buns and sandwich the burgers together.