Preheat the oven to 180 degrees C/350 degrees F/Gas 5.

Spread the cashew nuts on to a baking sheet and cook for 8-10 minutes, watching carefully as they brown quickly after about 5 minutes. Alternatively, use pre-roasted, unsalted cashews.

Heat the olive oil in a large frying pan.

Add the chopped red onion, grated carrot, chopped leek, sliced mushrooms, crushed garlic, and fresh thyme leaves to the pan.

Sauté the vegetables for 10 minutes until they are soft and the liquid has evaporated.

Add the cooked brown rice and cook for 1 minute.

Remove the pan from the heat and allow the mixture to cool slightly.

Place the roasted cashews in a food processor and pulse 6-7 times until coarsely chopped.

Add the sautéed vegetable and rice mixture to the food processor, along with the grated Gruyere, fresh breadcrumbs, clear honey, egg yolk, and seasoning.

Pulse the mixture 5-6 times until just combined.

Dust your hands with flour.

Form the mixture into 8 patties.

Refrigerate the patties for a minimum of one hour, or preferably overnight.

Heat the sunflower oil in a non-stick frying pan.

Dust the burgers with flour.

Gently fry the burgers for about 3 minutes on each side until golden brown.