To make the beet burgers heat the olive oil, add the grated beetroot and the thyme and cook for 5 minutes then leave to the side to cool. In a food processor mix the chickpeas, medjool dates, garlic, parsley, tahini, tamari and oats. Blend well then add the beetroot. Roll into 4 burgers place in the fridge for an hour to set.
Preheat the oven to 200°C.
Bake the burgers in the oven for 15 minutes.
Chop off the stalks and brush the mushrooms with the olive oil and season with salt, then place in the oven for the last 7 minute of cooking time with the burger.
Place the beet burgers with some tomato and lettuce inside the portobello buns. Serve with sweet potato fries.