Lentil, chickpea, cheddar and onion burgers

Ingredients

• 3 tablespoons olive oil
• 1 large onion, chopped
• 2 cloves garlic, crushed
• 1 teaspoon ground cumin
• 1/4 teaspoon cayenne pepper
• 400g can lentils, drained and rinsed
• 400g can chickpeas, drained and rinsed
• 1 tablespoon tahini paste
• 2 tablespoons freshly chopped parsley
• 1 large organic egg, beaten
• 100g fresh breadcrumbs
• 100g grated Gruyère
• 100g feta, crumbled
• plain flour, for dusting
• salt
• freshly ground black pepper
• burger buns
• shredded lettuce
• sliced tomatoes
• sliced red onions
• sliced avocados
• soured cream
• tomato ketchup
• mayonnaise
• pickles and relishes