Place the cashews in a small bowl and cover with water. Leave soaking for at least three hours. Drain, then place in the food processor for 30 seconds or so until they resemble breadcrumbs. Set aside.
In a medium saucepan heat the olive oil then fry the onion, celery, red pepper, garlic on a low heat for around 15 minutes until completely softened. Leave to cool.
Place the beef mince, sausagemeat, chicken livers, cashew crumbs, parsley, spices and salt and pepper in a large mixing bowl. Mix together to form four patties.
Place in the fridge for 30 minutes to rest.
Heat a cast iron skillet with 1 teaspoon olive oil then griddle the burgers for 5-6 minutes on each side.
Tuck the burger straight into your bun with crisp lettuce, tomato, red onion rings, chipotle mayo and cheddar cheese.