Vegan stack burger

Ingredients

• For the burgers:
• 400g can mixed beans, drained and mashed
• 1 sweet potato, peeled, boiled and mashed (250g)
• 1 onion, finely grated
• 1 tsp curry paste
• 2 cloves garlic crushed
• 2 tsp rapeseed oil, for frying
• Chargrilled veggies:
• half aubergine, sliced into 4 x 4cm slices
• 4 Portobello mushrooms, stalks removed
• 1 courgette, cut into long slices
• 1 red pepper, quartered
• 1 yellow pepper, quartered
• Salad:
• 8 little gem lettuce leaves
• 1 very large tomato, sliced
• 1 red onion, thinly sliced
• 4 wholemeal baps, split and lightly toasted (65g each)
• Sauce:
• 4 tsp tahini, mixed with juice 1 lemon and 2 tbsp water