Vegan walnut and black bean burger

Burger buns

• 1 tsp olive oil, for greasing and brushing
• 1 tbsp white sugar
• 2 ½ tsp dried instant yeast
• 220 g water
• 340 g baker's flour, plus extra for dusting
• ½ tsp salt

Patties

• 1200 g water, plus an extra 3 tbsp
• 1 tsp salt
• 100 g white quinoa
• 1 tbsp flaxseeds (linseeds)
• 30 g olive oil, plus an extra 1 tbsp for frying
• 30 g eschalots
• 1 garlic clove
• 1 slice bread, torn into pieces (3 cm)
• 1 pinch ground black pepper
• 400 g canned black beans, rinsed and drained (approx. 250 g after draining)
• 35 g walnuts
• 20 g tomato paste
• 2 tsp ground cumin
• 2 tsp sweet paprika
• 2 - 3 tsp poppy seeds

Assembly

• 70 g tomato sauce (see Tip)
• 4 - 8 green lettuce leaves
• 8 - 12 slices fresh tomato
• 1 avocado, flesh only, cut into slices (optional)
• 1 red onion, cut into thin rings (optional)